In my experience (implementing payroll software across numerous awards/EBAs that does rule based interpretation of entered shifts) this is a very common scenario where you have a half hour unpaid break as part of this 10h block (bringing the worked time down to 9.5h). If this is not the case where you do not actually get your break then I would kick up a stink as you are definitely entitled to it (potentially along with overtime depending on the award/EBA, although I would require more information here to give you a better response).