First, please activate trim and then zero the pitch gauge.
In trim, all servos are locked to the middle. Since we previously set zero pitch here, we can now zero the gauge here - no matter how crooked the helicopter is.
By moving the collective stick, the respective min/max collective values are activated. This setting is initially applied to all banks, but can later be individually refined with the collective curve. More on this later.
For maximum collective, for example, set the stick to fully positive and adjust the desired value. Here we should expect around 80...110 for the usual approx. 12°, this would be a good indication of the geometric design of the helicopter.
For minimum collective - it depends. With fun scalers it is of course symmetrical, with pure scalers the "end of the mechanics" can be at -5°. I would always set what is mechanically acceptable here - because the fine tuning comes later.