Symptom:
Issue in phone device's "Super Copy Configuration" page

Conditions:
Register a phone device to the CUCM.

For creating another similar phone 

Go to: 
The super copy option of the already registered phone.

Here it will ask for the MAC Address.

Enter MAC address as xx:xx:xx:xx:xx:xx

Expected Result : It should accept this value.

Actual Result : It is not allowing the user to go beyond 12 characters including the colon i.e. xx:xx:xx:xx:

PFA the screenshot for getting a clear idea.