Different serial numbers of U3014 monitor on the back panel and at the WMI

Hi, I'm doing an inventory of IT-equipment.

I got a problem with DELL U3014's serial numbers:

DELL Monitors have different serial numbers on the back panel and at the WmiMonitorID class.

For example, there is 20 digit alpha-numeric serial number, like CZ-0F525M-73608-021-341L, on the back panel and there is 12 digit alpha-numeric serial number, like F525M021341L at the WmiMonitorID class.

Why is this happening?

Is there any official document that explains this replacement of serial number?

I have no problem with monitors of another manufacturer.