Kanna's Kishin Skoukan Spawn Increase

Kishin Shoukan has a y = 70 variable, which could be the spawn rate increase they provide.

The original Japanese is
モンスターが出る速度も速くなる。
Which literally means "the speed at which monsters appear is made faster".

That' is great info. It would coincide with my findings. I had determined it was over 50% but not as high as 75% (rounded down to the nearest whole number).

Could the Y number refer to the skill's hit box though?