Hi there,
I agree with Brandon and Beth - wait until you get that paycheck and make sure you made at least minimum wage for the number of hours worked. (As Brandon said, it's calculated weekly, even if you are paid bi-weekly.)
If you are still below minimum wage, make a copy of your paystub and bring it to the attention of your manager - politely . Just say "I was reviewing my paystub, and I noticed I made less than minimum wage for this week." Show your math on the stub if it isn't obvious. As Beth said, the restaurant should kick in the extra - if they don't, you should leave, as you are legally in the right, but it will be easier to find a new job then bring a complaint.
This issue may be more complicated if you are not reporting tips to your employer. Hopefully you are! If not, you should start tracking your tips on IRS Form 4070-A, available for download on the irs.gov website.
Good luck!! :)