posted by rfvv .
1. They can understand new commands after only a few times.
(Does 'only' modify 'after a few times'? noun phrase...)
2. They understand new commands only after about 100 times.
(Does 'only' modify 'after abut 100 times'? adverbial phrasse...)
Yes, in both sentences, you have "only" in the right place for the very reasons you have written. Nice!