Yesterday I placed two separate orders of the same item. The seller shipped them together. I received an order update email:

As you can see, the same Order number is shown for both orders while actually these are two distinct orders with numbers:
20-10698-81843 (placed first)
08-10706-15935 (placed second)
The email template seems to output the order number from the first item for all items rather than their actual own order numbers.