According to Vehiclehistory.com, the fuel capacity in the 2004 Mazda Tribute is 16 gallons. You may want to check your manual to confirm. I have heard of gas stations fraudulently manipulating the pumps to overcharge the customers. Some States (if not all) have inspection crews to test the pumps looking for this type of fraud.

If you did not find a 3 or 4 gallon puddle of gas under your vehicle when you pulled away and your tank does not hold 19+ gallons the pump may have overcharged you as either an honest or fraudulent error. You may want to report it to the State I suspect that you (and every other customer to use that station) may have been ripped off. (the Department of Agriculture regulates fuel pumps in Texas)