I don't know wwhether this still works (AFAIK assigning CALs to devices was deprecated a while ago) but you certainly don't want to mix them. Either you assign CALs to identified Devices or you assign them to identified Users.
In general you assign CALs to IDs. Those IDs can be either User IDs (DSC validated identities) or Device IDs (Machine name + MAC Address).
The setting to switch your QlikView Server license assignment method from User ID to Device ID and vice-versa is on QMC page QMC->System->Licenses->QlikView Server (in tree view)->Client Access Licenses (CALs)->General->Identification. Switching to the other mode allows you to assign licenses to different IDs, while the older assignments stay put.
Keep in mind that Qlik publicly advises you not to mix Identification methods on a single QVS, as this may lead to double CAL assignments. So if I were you, I would follow Miguels suggestion and contact your Qlik Partner.