[Scott65]

I don't think he's adding due to his reset to zero function, he doesn't have to. You want the angle to be a very slight V looking from the side. Pinion down towards the ground relative to the driveshaft(negative). Go back and watch Tim's video, paying special attention to his explanation using the "V". If your inclinometer doesn't have the reset zero function like his, then just keep in mind the "V" scenario he lays out. He shows how he tips the tool to verify which direction brings it to zero, and which way its leaning.
Edited to add: if your pinion yoke isn't machined like the one he shows, Ive used a socket that fits the bearing cap to put the measuring tool on to make sure its flat and accurate.