1099 understates actual sales activity

Hello, I started selling in December and had a lot of sales activity the last couple days of the year. Just received my 1099 and followed the instructions it contained to compare to my sales data. Looking at just the product sales column, the 1099 says $8,300 in December but the product sales column in the monthly transaction report says $10,750. If I filter to exclude December 31, then I get to $8,200, which is a lot closer to what’s in the 1099. Does this mean the 1099 is not picking up the last day or so of sales? Maybe there is a difference between the date (e.g. December 31) an order was made by a customer and the date it was processed (e.g. January 1) and is counted in the 1099? What should I do here? I want to give my accountant the correct Amazon fees and shipping costs (all purchased through Amazon) for deductions? But I don’t know how to get those numbers correctly given this mismatch.