I have a problem understanding instructions in the manual. To create Soft Mute for example, we have to create joystick assignment for PROPELLER SYNC (ON/OFF). The confusing part is that the instruction for Secondary Button is to also create joystick assignment for PROPELLER SYNC (ON/OFF). The same thing with Hard Mute and Main Button. The same assignments for two different functions? Is this how it should be?

Yes, it's correct. 

The assignment is the same for both functions.

Voice and Button control function separately, so it's okay to use the same assignment in that context with no problem since the respective functions are different.

Cheers,

I understand now.