I was just guessing at the differential --they can be adjustable from 5* all the way to 25* on some units -- most are 10* to 20*
I had mine set @ 5* for the last year -- seemed to fire the boiler too often. I might raise the temp & set the diff to 10* to see how that works. Mine is adjustable from 5* to 20*, plus if it's set over 5* you can then set a "pre-heat" setting that kicks on the circulator for a set time before firing the burner, and the "post-heat" that will leave the circulator running for your set time to pull excess heat out of the boiler after burner shut-down. I haven't played with the settings in a while & decided to experiment a bit with them, since I've been in the basement for the last 2 days straight!