Devices need not be mapped initially. Any login would be detected and the device will be registered in the web app for unmapping actions later when needed with respect to the number of licenses purchased.
Settings:
->Registered devices
If the employee/ the device used for stock take is not available , kindly go to settings-> registered devices-> unmap the device which is not in use by unticking the check box. the next device that you login, will automatically get mapped here .