connected devices show up with different name after being assigned

After assigning devices to different users the next day the same devices show up as unassigned devices with the same name but followed by a 3 digit number, per exampel Sams-iphone and Sams- iphone-372. Since the new sign up are not assigned they are not getting paused at bedtime....

any idea why that happenes and what the 3 digit number means behind the name?