Highest point to lowest point. And as the boys say, bleed calipers with bleed nipple to the top. Sometimes you have to swap calipers side-to-side or front-to-back, so you have to bleed them with the calipers detached from the backing plates, but pushed onto the disc, so that you can keep the bleed nipple pointing up.

No Lobster..this isn't time to paste a "nipple" into the thread..

Chris