Can someone plz enlighten me about a cars gas tank

So my sister has a 2020 se corolla. I looked up and it said she has a 13.2 gallon gas tank in her car. We’re coming home the low gas light comes on at 15 miles left cool we go to get gas. The display said it had 4 miles left before empty when we pulled up to the gas station (now I know you can drive for about a few miles after the zero hits). The car filled up with 10 gallons. Giving us a range of 270 miles on the display. So my question is what is going on? Does she have a 10 gallon tank? Is this normal?