Limiting Reactants: on a video my teacher made, he said 4 H2 + 100 O2 = 4 H2O

However, later he said,

15 H2 + 12 O2 = 7 H2O

Wouldn’t it be 15 H2O because H2O consists of H2 and a single O atom? In the equation there are 15 H2 and 24 single O atoms. Did my teacher make an error, or did I?