The most likely scenario is that they just make up the number for the fragments and the damage, and did not check if it is even possible for the shell to create that many fragments with the energy they have.
Actually the funny thing is, you can find a similar damage distribution between various APHE shells.
For example the czech 37mm guns on the Pz 35/38s have 2 almost identical APHE. One with a tracer (and 1mm less pen) and one without. The one with the tracer is almost the same mass as the other, has identical filler mass and type, yet it does many times more damage than the tracerless. Similar goes to the damage difference between the japanese/soviet 47mm compared to the italian 47mm.