There seems to be an issue with counting

I ordered two batches of stickers one at 30 and this design in 20. The over all quality of the stickers is great and better than I expected but instead of 20 for this design I got 24. normally this would be fine, I mean who doesnt love free stuff? The part that bothers me though is that the other batch of 30 only came with 29 and one of them was messed up anyway.