The first and most important information what's also on our Pricing page:
How do we calculate the extra sales?
A sale is attributed to Recart if a customer opens or clicks a Messenger notification sent by Recart and makes the purchase in the next 72 hours.
In certain cases, when sending Recart automated messages, Facebook will not provide us information about whether the recipient opened the message. In these cases, the 72-hour conversion window will be open when the user received the message.
The Extra Sales is the most important metric in your Recart account. Not just because that's money, but because it also determines your monthly Recart plan cost.