It’s PPM in inkscape layer name 10 [ feed=1200,ppm=6] is 10 power, feed 1200mm/minute with 6 pulse per mm
For Air Assist I use a vane air pump off a old select comfort air matteress. I’ve engraved Granite (bad Robi! burned up a tube) cut 1/4" plywood 6 passes at ~ 20w.