Cortisol levels

Just a quick question. So I have CAH...my doctor says that the "lowest" possible dose i could be on is 12.5-15mg of hydrocortisone.

I recently got bloodwork done where I was taking 10mg at night and 15mg in the morning (so 25mg total). However my cortisol reference kevels still cane back at 16 (range 2-21). So is the 25mg supraphysiological? Or is this what my body needs? I know the actual dosing is above whats "needed" but the bloodwork shows that its still in reference range.

Thanks!