Just lost 200 and might be fired

I work at a fast food place and at the end of the day we count our money. We then subtract 200 and place the 200 in the cash register.

My expected cash was 700, I had 700$ in total. You have to subtract 200 and place the 200 in the till since that's our starting amount.

So as usual subtracted 200 and got 500, meaning I'm missing 200. Meaning I was suppose to have 900.

I don't know what to do, I'm so scared my boss might think I stole or somehow lost 200 dollars.

Idk what happend and I'm so scared, I need the money for college so I can't get fired.

Noi dont mind paying the money back, i just dont want to get fired. I have to wait till tomorrow to talk to him about it and I'm scared he will say I actually do owe 200 and will fire me.

I can pay the money back no problem but I'm just worried about the consequences.

Also how should I even tell him tomorrow. I don't just want to say "yeah I may have lost 200 dollars"

Edit: Just told my manager, he said he'd review it later since he's not at work today.

Edit: I'm a dumbass, during my sleep deprived stated i thought I was missing 200. I was not and was totally fine.