Count as 1 pop count
Any standard miilitary unit
tree spirit thingies
all siege units
Dragons G-6, R-8, Royal-10, ice/haunter -10 i think these are right
Most elites -5 +/-
Delete some units to make room for 10 so you can place you wizard. I think the numbers above are right, on a new city so cant check the numbers.
So if you are 90/90 in your city you will have to remove units that equal 10 to make 80/90.
If at 81/90 remove 1, 85/90 have to remove 5, etc...........