There should be a decoder ring on their site <g>. Actually they should have the described names there.
In a nutshell, PK is Photo Black, MK Matt black. Since the profiles had to change over various versions, you'd use 6 with version 6 of IP (and I assume later). Then you have different profiles based on the lighting under which you'll view the prints (Day for daylight, RCWF is a Fluorescent light etc).