FM8 question

Hey there! I have a question about FM8. This is probably a dumb question, but I could use the help. On the expert tab, when i try and change the operator levels, such as like operator b going into operator a by 100, the sound doesnt change. I’ve been trying to do skrillex growls, and from watching videos, when everyone else changes levels, the sound changes. Like i said, mine just sounds the same. Thanks!