First number: Which category does the subforums belong too?
Second number: Where do they belong, 0 means its a root forum, 1 is subforum to 0 and 2 is sub to 1

ROOT1		1,0
|sub1            1,1
 |-sub2           1,2
 |-sub3           1,2
  |-sub4          1,3
ROOT2		2,0
|sub1		 2,1
 |-sub2           2,2