MAX setting is for FULL burn without pushing hot coals off the end of the grate. It varies by stove and setup. whatever the manual suggests for a starting point is usually pretty close.
When it's calling for heat and it gets up to FR99 and the setpoint is not achieved, and you still have 1" or more of ash at the end of the grate, you can increase the MAX a couple points until you achieve the 1" or less of ash at full burn. you don't want hot coals pushing off the end, it's just wasting coal.
Depending on where your thermostat is located in relation to the stove, will also have an effect on how quickly it responds. of course, coal takes time to respond. depending on how much temp change you have, you may always get a little overshoot until it settles down. sometimes it's unavoidable depending on the situation.
Theres also some fan settings (CFM) at a certain feed rate, etc.... you can play with to get the heat moving quicker.
If read the manual and look on here for explaination of the terms. V3 firmware features