Not all available slots in overlapped resource groups are allocated to my application. Why?

If a host belongs to more than one resource group (because of overlapping in resource group definitions), the host from only one resource group is allocated to the application. If the host is already assigned to the application (allocation) from one resource group, the host is not assigned to the same allocation from other resource groups. This host from other resource groups, however, can be allocated to other applications which do not have the same host allocated.