How do the zombies ranks work?

[jjk]

I feel like the zombies ranking system in plutonium works different than the zombies ranking system in bo2 itself. But how does it work?

I got a few friends that have forever been single bone rank while I am on this rank right now:

Can someone maybe explain how the ranking system works? would be appreciated B)

[luigistyle]

It works only in Custom Games or Solo Play.

[jjk]

luigistyle yeah ok but so it's the same as the actual game or?

[luigistyle]

jjk I assume so, yes.