Start with the full campaign total
Performance Max can serve beyond Shopping inventory. GMCMax compares campaign totals with product-level reporting and shows the remaining spend or reporting adjustment separately.
Match the offers Google reports
Offer identifiers, Shopify product and variant IDs, SKUs, and barcodes help match reported Shopping spend to your catalog. Ambiguous offers remain unmatched instead of being spread across products.
Keep revenue definitions visible
Shopify product sales include all channels. Dividing them by matched Shopping spend produces a product-level blended ratio, not proof that PMax generated every sale. Use Google Ads conversion metrics when reviewing Google’s attributed results.
Act with the right expectations
If you activate the optional feed automation, it unpublishes qualifying products from Google & YouTube only. Shopify product status and other channels stay unchanged. Feed eligibility can take time to update; this is not an immediate pause of a PMax campaign.