You open the campaign and the Conversions column says 48 for the month. Your store says 11 orders. Nothing is broken: the campaign counted exactly what you told it to count, and it has been spending your budget on more of the same.
Primary or secondary: the setting that tells Performance Max what to hunt
Google splits every conversion action in your account into two kinds. Its help page puts it this way: primary actions are "conversion actions that are reported in the 'Conversions' column in your reports and used for bidding." Secondary actions "are for observation only. They are used for reporting in the 'All conversions' column in your reports, but not for bidding." Source: About primary and secondary conversion actions.
Mark add to cart as primary and the campaign goes looking for people who add to cart, which is easy, because carts are cheap and frequent. The Conversions column grows and the cost per conversion looks great while revenue stays where it was. Page views, phone clicks, newsletter signups and the "view item" events that Shopify and GA4 pass into the account work the same way if you let them count.
Purchase, or the one lead that becomes a client
For an online store that is the purchase. For a service business it is the lead that turns into a client, in whatever form that takes for you: a quote form, a booked call, a phone call from the ad. Pick the action you would happily pay for on its own, and set everything upstream of it to secondary: add to cart, begin checkout, add payment info, product views, phone number clicks, email signups. They all stay visible in the All conversions column, so you lose nothing in reporting. The campaign stops bidding on them, and that is the whole point.
Google also notes that "most conversion actions can be set to either primary or secondary, but some conversion actions aren't able to be set as primary or secondary." If the switch is missing for one of your actions, Google has locked it. Open the goal that action belongs to in your Conversions summary and work with what you can change there.
Doubles and custom goals
In Shopify accounts I see the same duplicate over and over. The Google & YouTube app creates its own purchase action. Then someone links GA4 and imports the purchase event from there, and now two actions fire on every order, both sitting in the Purchase goal as primary. Every order counts twice, and the campaign bids as if your store made twice the money it did. Keep the action whose values line up with your store's order totals and switch the other one to secondary. Leave it in the account, because you may want its history later.
Custom goals are the other place to look. Google's help page is direct about it: "Conversion actions included in a custom goal are used for reporting and bidding regardless of whether they're set as 'primary' or 'secondary' actions." A campaign that runs on a custom goal bids on every action inside that goal, secondary or not. Open the campaign settings, find the Goals section, and check whether the campaign uses the account default goals or a custom one.
The Conversion action segment
In the Campaigns table, click the Segment icon above the table, choose Conversions, then Conversion action. Each campaign row splits into one line per action, with the count next to it. If the campaign shows 48 conversions and the segment shows 11 purchases, 29 add to cart and 8 begin checkout, your primary setting is wrong, and the campaign has been spending on carts. If the segment shows 48 purchases but you had 11 orders, look for duplicates: two lines with "purchase" in the name, similar numbers, both counted. I also keep the All conv. column next to Conversions; a large gap between the two means most of your tracked actions are secondary, which is how it should be.
To change a setting, go to Goals, then Conversions, then Summary. Find the goal that includes the action, click Edit goal, and in the "Conversion action optimization" section set each action to Primary or Secondary (observe only). Save. Those are Google's own steps from the page linked above.
From that moment the Conversions column shows only the primary actions, so the number drops to what the store can confirm. The campaign also starts learning from a different signal. I can still adjust the budget in that period, because the campaign keeps spending the way it did. What I don't do is switch it to another bid strategy, and I give it three to four days before I judge the result.
If you have twenty minutes this week, open Goals → Conversions → Summary and count the primary actions in each goal. More than one, or a primary action that is not a sale or a real lead, needs a closer look. Then check each campaign for a custom goal, segment the campaigns table by Conversion action, and compare the counts with your store's orders for the same period. Whatever you change, leave budgets and targets alone for a couple of weeks afterwards.
My tip: I keep one primary action per account: the purchase, or the one lead that turns into a client. Everything else is secondary, even when a client wants the report to show more conversions. And once a week I open the Conversion action segment and check what each campaign is counting. Five minutes, and a "great month" that the bank account doesn't recognize stops happening.
If you fix the primary action and Performance Max still spends on the wrong things, the problem sits deeper in the setup: asset groups, product feed, brand traffic. I wrote a full guide on why Performance Max campaigns fail and how to fix each cause.
