I beleive on the last 8.0 update (r3) that they gave us the ability to be able to save differnent intersection groups as part of a layer combination. Make sure that you hit update in the combination layer if you change your intersection numbers. It should remember then. This new scheme is a mixed blessing.
I believe there is not any significance to the number themselves, they are just for grouping purposes. I'm glad I could help.
I like the new setup, but it was a killer when I upgraded from r2 to r3 to my existing projects. I had to through all my layer setups to fix the intersection groups. Just a minor complaint, otherwise it's a great addtion when used in a template for new projects.