Assignment of work to Resources

I have recently learnt how to Assign hours of work based on an activity for a resource, however here is the issue I can't seem to sort out.

If I log in as the original ADMIN user (administrator) I can ADD, EDIT and DELETE assignments on all activities. However if I change one of my Staff Members profile to Administrator, he has all the rights as an Administrator, but he cannot ADD, EDIT, DELETE an assignment on an activity.

I have looked through all the Access Rights and Administrator has it all active and YES etc, but it the contacts that have the profile of Administrator cannot actually do the assignments.

What am I doing wrong. Your help is most appreciated.

Thank you.