Due to the fact that MyAllocator is a bit more flexible than a regular booking portal, and it allows you to set up the pricing for private rooms either per person, either per room (see here).
The settings in HostelSystem can also be made in multiple ways, depending how MyAllocator was pre-setup.

For instance, if you set up your MyAllocator to per room:

 you can set up HostelSystem room pricing to per room:

Afterwards, in MANAGE / ONLINE PORTALS / MYALLOCATOR / ROOM the private room should be set up this way:

Contact us if you have any doubts, so that we could help you.