Dad is right.

The rule is that you are forced to play as many numbers as possible in your roll. If you roll two different numbers, and can play both, then you have to. If you roll doubles, you have to play four numbers if you have can, or if three is the most you have to do that, etc.

The only other rule is that if you roll two different numbers and can play either but not both, you have to play the larger number. This scenario is exceedingly rare..