Like they stated, always start with the temp at or below the room temperature until the stove it up to temperature, then raise the temp a few degrees at a time until it catches up,
COAL is SLOW in responding, it's not like a gas or propane furnace that is almost instant and can heat up fast in a short period of time. The CoalTrol will keep raising the feed rate to make up the difference in temp, so a large swing in temp from room temp to setpoint, will make it raise faster and possibly overshoot, then takes a while to cool back down....Depends on how far away your heat source is from your thermostat.
Once you get the temp up, I wouldn't change it too much, maybe 2-3 degrees at a time.
I usually just leave mine around that same temp or 1-2 degrees different, so it doesn't have big temp swings...Takes a bit, but you will get it dialed in and it will maintain temps.