I just got back from a week-long business trip with my company.  This is the first time I've traveled with my current company.

On our trip, we had a $300/day meal allowance that we would charge on the corporate credit card.  Being a big foodie and traveling to a city known for its fine dining, I was thrilled!  I didn't max out my daily allowance, but I went all in on meals.  All-in-all, for 7 days, I ended up charging about $1,550.

Well... I filled out an expense report today.  When I re-read the rules in closer detail, I see that the meal allowance was actually $300 for the entire week (not per day)!

So, obviously I screwed up royally.  I'm complete idiot.  I feel like I'm about to throw up.  I would normally just offer to pay up the difference out of pocket, but money is really tight.

I'm afraid I'm going to get fired (and probably rightfully so).  What's the best way to bring this up to my boss?  Is there anything I can say or avoid saying to minimize the damage?