Ok, not only did the gas station attendant enter the wrong amount - 33.156 is for liters, not the charge of 24,900 pesos (about $52.00) - he entered an extra 3. So my credit card was charged 333,156 pesos for gas - a mere $701.00!!
They tried to reverse the charge but were unsuccessful. After the manager came (that is him kneeling down trying to get the credit card machine to issue a refund) and we had waited for an hour they finally gave us cash. They only charged us $18 for the gas. They were very apologetic.
The moral of the story is - make sure you have enough gas Saturday to handle anything that may come up on Sunday.