Mob spawning issue

So, I'm working on a mod and made mobs for a dimension, but the mobs seem to always spawn underground, and almost NEVER on the surface.

They successfully spawn in the dimension, but it's always underground, and I would like to make it so it spawns equally on the surface and underground.

I've tried doing:

--

Natural entity spawning condition,

 if [y > 60] , return true

 do

 return false

--

But that didn't seem to work at all, I've been trying to make the spawning through the biome and or the mob, doing both at the same time, and then other times just the mob or just the biome, but everything I tried didn't work.