Currently it is difficult to restrict the "Billable" hour type to just one group of users. Under the section "Define Availability at the User Level," it explains that you can select or leave unselected certain custom hour types on an individual user-basis, but that if you leave all hour types unselected, it functions the same as selecting all of them. It works the same at the Project level. Either users can see all the custom hour types, or only a selected few hour types, but never none of the custom hour types. We would like the ability to restrict "Billable" hours to specific to one group of users rather than all the groups.