NO, they are NOT pre-calibrated, every stove setup is different. The Field Controls RC, most of us use (http://fieldcontrols.com/rc.php
) has the scale on it to get it close when setting up it initially. Usually once or twice a season they need to be checked/calibrated. Many of us keep the manometer hooked up all the time and can easily tell what the draft is.
You should/need to calibrate it with a Draft Gauge (Manometer) with a good hot fire, so it can maintain the proper draft on the stove and pull the required draft when really needed on a full burn. There is no other SAFE way to calibrate it, you don't want CO leaking into the house!! It will open/close more when it 's windy, but that will maintain the proper draft on the stove and not pull more air thru it and loose more heat up the chimney.
Read the threads on Baro Install and MANOMETER install for more info.
The Blower plate is factory set at about 1/2 open on the Keystokers, that will adjust your burn, more ash or more clinkers (fused together, too much air), etc....usually you don't have to mess with that at all, but it will change the draft if you change the plate setting, then you have to readjust your baro slightly.....
It's not too complicated, once you do it once.....and read up on how to do it.