Editing Security Roles in CRM

Hi,

I have created a new custom entity in CRM 2013. I want to give access to users to that entity records based on the BU level and user level. When I click on any existing security role and try to update it, I can only provide access for the whole organisation level or None. I cannot give access to BU level or User level. 

I even created a new Security Role and tried editing for that entity at the BU level but to no avail. I can provide for the whole Organisation level (full green) or None (empty).

When I click, its full green and then when I click again its empty. Again the same. Where are the yellow colours?

What I am missing??Please advice