GDPR laws will limit the ability of our tool. Outside of U.S. the match rates are 15-45% across accounts, unfortunately usually on the lower side depending on lots of factors. Compared to U.S. where the average is 70-75% match rates. "Audience" is for audience only that pulls in your Amazon customers.. For the "purchases" it's ALL Amazon data regardless how the sale happened, then after that is when matching happens then after that the attribution happens.
"Audience" pulls back historically that's why that number will be larger, also Facebook only shows numbers in the Match and Attribution for high volume, so you won't see anything there unless it's like 1,000+ every 7 days. Attribution is shown at ad level regardless of volume.