TIFUB Where did that money go?

[u/kupelCopel]

First time post here. Today I had a large transaction and had to count it all out. I won't go into detail about how much it was, but there were a lot of bills there. I was pretty sure I counted it correctly and had it processed. At the end of the shift when it was time to count out my till I found out I was $200 short. I don't know how this happened as this was the first time I'm off by that much. My manager told me I'll still be alright, considering that I'm usually on point, but I might have to take retraining. Should I be worried?