By default, when checking out devices to users you will get a warning pop-up if a user already has one device assigned to them. However, administrators can change the number of a devices a user may have before receiving the warning in the check-out screen.
To do so, the admin will need to select Site Options from the Administration options in the left navigation bar. On the Site Options page, look for the Assets section located near the top of the page.

Scroll down until you see the options for Number of allowed assets to be assigned before warning. From here, you can select the warning values for non-student and students users independently of one another. Once completed, remember to click Save at the bottom of the Site Options page.