There are three possible states in a privilege checkbox:
Unchecked - it indicates all selected roles have the privilege(s) revoked/unselected on the specified object(s).
Checked - it indicates all selected roles have the privilege(s) granted/selected on the specified object(s).
Indeterminate - it indicates the privilege(s) of the selected roles are a mixture of checked and unchecked values.
Note: Indeterminate state appears only when you select multiple roles.
Note: Privileges which are not applicable to the selected type of objects are greyed out.