Facebook receives data from Amazon as soon as an order is marked as "shipped". Zontracker is working in the background every 5 minutes to process data.
Even though some sales attribution may show up right away and same day, some of the data trickles in the next day and the days after.
We are dependent on Amazon fulfilling the order (or manual fulfillment), which is also typically slower on the weekends.
It's a good practice to check your data as soon as you can to make ad decisions, but also set your schedule to make more accurate interpretations multiples times (such as 3, 7, and 28 days later) to account for the delayed attribution.
It's common to see about 25-50% of the data come in the same day (that means someone saw/clicked your ad, purchased on Amazon, order was processed and fulfilled), while 50-75%+ of all data is in 0-3 days, and 75-90%+ of the data by day 7 after seeing/clicking ad. We are not referring to sales attribution here (that is in the next support article) but simply % of orders across accounts how fast Amazon ships orders.