record level security

i have to assign a user to a particular customer group i hv run the record level security wizard it asks me to select a role tht u want to do setting i select a role say accountant then i select the table named customer group then i went to query button & put tht particular customer group with tht table. Now whn i assign tht role (accountant) to a user he shud hv been restricted to only tht customer group but its nt the case he can see all customer groups why?? i dnt understand can anybody help me

Can you please check whether the same user is assigned to different groups other than the one you created.

Apparently, security is Union of the roles assigned to it.

no that user is only assigned to one user group n no one else group