You should be doing custom conversions and track it with a second system - GA or your own datalayer push. It do the attribution side by side. "So just by reading a comment FB is claiming credit, even if FB never was the means that led customers to the ecommerce site. Is anyone else seeing these kind of discrepencies? " This is the problem with attribution. Who takes the credit? If I am on my phone, see an ad. Then a day later, without clicking on an ad but going to a link directly on my desktop, some systems will count that original phone view as the source attribution. Because it knows my user profile already. Doesnt matter if I am on a phone or desktop, both devices are linked to that user. So if I clicked on a Google Search, FB will also try to claim credit.