You're not gonna like this but .... Forget the books. Do you own math.
Look at the room, how many tables, how many hours open, what would the monthly number be if the room was running at 100% for the entire hours open you calculated.
Now, take 25 % of that as your realistic income. Put that number in big type on the left side of your paper.
Now, add you monthly salary, and your employees monthly salary all the rent and utilities, every other expense you can figure, then add an additional 10% in for fun.
Subtract that number from that number on the left, and then forget the whole thing. But that's just my opinion.
Or, to figure it another way, I wouldn't be happy unless my rent was $200 dollars a month x the number of tables in the room. Not a penny more.