The number of bolts refers to the number of bolts holding the ring gear to the diff center, and the number of pins refers to the number of what I will describe as "diff pinion" or "spider gear" axles ...
This picture shows the internal gears of a differential - you can see the two "side gears" (which are top & bottom in the picture), and the other two gears are known as diff pinions, or spider gears - as you can see they are on a cross pin or axle - that is the diff pin.
Differentials can be built with two, three or four diff pinions (with two & four being the most common) a two pinion diff will have a single cross pin (as shown), a three pinion diff will have three pins which meet in a central support block, and a four pinion diff will typically have three pins (one long & two short) that also meet in a support block.
The pin count has nothing to do with the small pins & springs in the lockright - all four of those will be used.
Just to add to the confusion, some so called four pin diffs only have three pins, and two pin diffs in reality will only have one.