As of version 3.15.xx it is possible to create allotments that are directly deducted from the availability, without being sold already. This was not possible and is still not possible on allotments that are configured using a virtual room type. However, if a ‘fixed’ room type is used in the allotment agreement, it is now possible to add this feature.
On existing allotments it may not be possible to edit this feature, since the allotment might use the virtual room type.