I need to replace an existing toilet. I am confused by the terminology found at the local Home Depot. The new toilet says "rough in" 12" and distance from wall 30 3/8".

I thought I read somewhere that you measure to the center of the hold down bolt to the wall. My measurement there is 12 1/2". The distance from the wall to the front of my toilet base is about 22".

Where should I be measuring from and do I need to worry about the distance from wall measurement being so long compared to my current toilet? Help!!