Gain1 vs Gain2

This pertains to both the Nameless Suite and the Cali Suite but I’m having trouble trying to figure out the difference between the two Gain knobs. They both seem to be doing different things from each other but I can’t seem to figure out what they are. I also know that dialling Gain2 lower will make the tone brighter, and while I like bright-sounding guitar tones, these amps tend to start sounding harsh rather quickly and I can’t dial the tones in a way that they sound bright wothout killing my ears. It’s either that or the guitars sound too clean and the amp doesn’t sound like a high gain amp anymore. What do these things do?

Note: I’m playing 9-string guitars.

From the owner’s manual:

"GAIN 1 KNOB (OD1 & OD2 ONLY): Controls the amount of gain in the preamp section.
GAIN 2 KNOB (OD1 & OD2 ONLY): Sets your 2nd gain for OD1/OD2 channels with the dedicated 3-way BRIGHT switch. "
I’m fairly certain that in the real amp Gain I feeds into Gain II, so it’s safe to asume one affects the other.
Might be worth checking the owners’ manual of the real deal: https://www.fortinamps.com/wp-content/uploads/2019/05/CALI_OwnersManual.pdf