Your PTG installer will have set your transmitter (hip pack) gains at the time of install along with the other gains in the system. You should not need to adjust these.
If, however, you are experiencing drop outs, static in the voice channel, or otherwise poor sound, note that the gain dial may be set too high. Generally, this setting should be the lowest possible point where clear audio can be heard.
Call your PTG support team at +1 (844) 639-6608 and we'll walk you through adjustments on this control.