That sounds like .020, (if there are 5 lines between zero and one, it would be .020 per line. 10 lines would be .010 per line)which should be about right if that is a stoker running low to mid range. A hand fired would probably be happier with a little more draft. When cranking the heat out, you may be up around .04-.05. You should set the baro to the manufactures specs for that unit.
I think your fine with 40#, I'll burn about twice that at those temps in my boiler.