Don't worry about it. The sign was likely referring to the bar area of the establishment. There are a lot of 'mixed use' businesses around.
One example - Hotels - The bar is required to post the 51% sign, but it only applies to the bar area of the hotel, not the entire property. How well the proprietor segregates the bar area from the rest of the eating/dining areas is often poorly executed.
Disclosure - I am not a lawyer, and did not sleep at a Motel 6 last night
I hope that you enjoyed your time here in TX regardless of the silly signage issues.