Why are shipped orders higher than fulfilled orders?

Is anyone able to explain how the numbers in the “Fulfillment over time” report are calculated? For some reason the number of shipped orders is higher than the number of fulfilled orders, which doesn’t really make sense to me. Is Shopify maybe counting orders that shipped in more than one box as 2 orders rather than 1? It’s the only thing I can think of, but I can’t find an explanation anywhere.

Edit: Upon further inspection, the numbers in the report are also completely off. I looked through my orders for a given period, and when going over them one by one and counting them by hand, there were 81 orders placed and 74 orders fulfilled (7 orders were canceled for various reasons). When looking at the Fulfillment Over Time report for the same time period, however, it shows 60 orders fulfilled and 66 orders shipped. Where are these numbers coming from?