Correct, the axle gearing ratio has zero to do with the number of ring gear bolts or cover bolts.

The most positive way to figure out the ratio is to remove the cover and count the number of teeth on the ring gear and on the pinion gear and divide the ring gear count by the pinion gear count. There is another method (that will get you close) that involves rotating the driveshaft by hand and counting the revolutions of the tire. If the rear axle has an "open" (or non limited slip) carrier, the procedure requires that one tire is held from rotating.....you can probably Google to find a more detailed instruction.