Damage low end to high end??

Wizardry

Something has been really baffling me on the damage calculations.

I assumed a number for example of 10-50 means i  can do that much damage on a normal hit.Now i have a support gem adding 1-13 damage,so i would assume 11-63 base damage right?

Are those numbers already including Critical damage?

I ask because when trying to figure out how the game got my actual damage numbers ,it never adds up.

Example if i have 10-50 and i have a 12% and a 18% and a 15% increase numbers would that not mean  an added 45% damage?

SO i have 11-63 base then adding in 45% more would make it 15-90 or close to that?

SO i hover over my spell i was checking and  the low number seemed to be kind of close but off a bit like 13 however the high end was 149.

Are the % rounded up or down and how did i end up with such a high end number,that is why i was thinking it is the max if i critical?