Problem summary
Your Ecommerce purchases total in Funnel can be higher than the Google Analytics 4 (GA4) total when your data source includes Item name.
Error message or symptoms
The total for Ecommerce purchases is too high.
Individual purchases appear in more than one item row.
The total decreases when you remove Item name.
When does this occur
A purchase contains more than one item.
The data source combines Ecommerce purchases with Item name.
You add the purchase values across item-level rows.
Root cause
Ecommerce purchases is a purchase-level metric. Item name creates one row for each item. A purchase that contains several items can appear on several rows. If you add the rows, you can count the purchase more than once.
Solution
Remove Item name from the data source that you use for purchase totals.
If you need item-level reporting, create a separate data source that includes Item name.
Use item-level metrics in that source instead of adding the purchase-level metric across item rows.
Filter downstream reports by data source to keep purchase-level and item-level values separate.