Item Release VS Overall Release

I have 2 release strategies, overall release (release group 02) and item wise (release group 01), the overall for non-stock and item wise for stock items. Is it possible to have these 2 release strategies in the system, because the item wise already existed and I just configured the overall. The problem that I have with the overall is that it only picks up the first 2 strategies irrespective of the different cost centre. I checked the strategies, Cl20n, Cl30n, and everything looks OK. the characteristcs that I have is Accnt Assignment, Cost Centre & Amount. What else can I look at or do top make this work.