I don't understand how the Map Attribute, Monster Qty is used.

I'm generating random maps using the gen text entry in the level.txt file. I'm following the example set for the mines. I've got a master map, Mine. That map has Monster Qty defined (20 - 0). I've got a sub-map named mine00 (starting location). I've got a sub-map named mine01 (default map attributes) with Map textures for the random map filler. I've got a sub-map named mine01a that has Monster Qty defined as 1 - 1.

Based on my experiments, the sub-map values are ignored. The only value considered is the one for the master map (mine). However, the values for Monster Qty are not used in the way I'd expect. Leaving them at the default of 0-0 and running /nummmonsters reveals that there are 12 on my level. Setting the value to 1-1 reveals that there are 20. Setting the value to 2-2 reveals that there are 24. Setting the value to 20-20 reveals that there are 52. I'm just not sure how this value is used.