On an open rear end, you have to multply the results by 2 because the differential will cut the ratio in half if only one wheel is turning. In Don's case 1.775 x 2 = 3.55. This may not be exact, but will give an approximatation that you can relate to available ratios. Hence the difference your shop guy claims.

If the rear end is a positraction/limited slip/traction loc/spooled or whatever then your count will be the actual number of turns, but you are not going to be able to turn one wheel easily with the other wheel on the ground.

If you have the rear end apart, divide the number of teeth on the ring gear by the number of teeth on the pinion to get your ratio.

Pat