pinion angle question again

ok folks i'll try and explain my spec.'s and tell me what you think.
putting a cheap harbor freight degree finder on the flat spot of the rear end yoke with it being parallel with the floor 1/2 tank of gas and driver in the car i get a 7 degree reading. when i mount the fixture on the input yoke for the trans i get 2 degree's. now both reading are on the same side of the dial so i can't say positive or negitve for either reading. so i have a total of 9 degree's between the 2 readings. am i in the ball park or do i need shim's to help for a better setting
thanks
terry