In the JumpCloud Administrator Portal, when you select "Systems" in the left column, you will find your systems listed in a column titled "System Name." The names in this list correspond with a field titled "Display Name" for each system, which you can see in each system's Details tab.
The Display Name is captured once when the JumpCloud Agent is installed on a system. The Display Name is not dynamically updated after that initial capture, but that field is editable, so you can change the Display Name of a system at any time.
Further down in a system's Details tab, you will find a line item for "Host Name". Host Name is updated dynamically at regular intervals, and you will see a Host Name updated within two hours after a change locally on a system, presuming the system remains online. There is not a mechanism for forcing an immediate Host Name update in the JumpCloud Administrator Console at this time.