Wannabee1999
when do you add or subtract this number from your HDG?
Just think about it. You don't, you add or subtract if from the Track to find your Heading. All headings and tracks are measured clockwise from Nortrh. If the drift is left The track will be left of the Heading so if you want to stay on Track, you must increase the Heading. Put simply, you must turn the Heading towards the wind to maintain the Track.