I find it most simple to use a 25" long riser as the benchmark and subtract.
on a 25" riser
Long Limbs: 70" Bow
Medium Limbs: 68" bow
Short Limbs: 66" bow
These limbs are made different lengths not with not so much thought of the overall length of the bow, but the draw length of the shooter.
Most are designed to be in the sweet spot of the limbs at a certain draw length.
I.E: Medium Limbs are designed for a 28" draw, shorts around a 26" draw and longs 30". Extra longs beyond that.
So, if you have a 28" draw, and want a 62" bow,
Medium limbs with a 17" riser, may be a better shooting bow than longs with a 15" riser.