I thought why not start a Skyrim AAR thread similar to what the old BSF had for each TES game and sometimes I miss those threads.
Anyway, yesterday I notice a number right to the legendary symbol for a skill in-game and after checking the actual skill in question I concluded that my currect skill level was high enough to let me unlock two other skill levels hence the 2 number.
As you can see I can, if I wanted to, use two perks for level 25 and 30 as my current level is 36 for the alteration skill.