Source List - Importance of Number ( EORD-ZEORD) field

Hi,

while migratng the Source List I find the filed " Number" in the EORD table ( Field - EORD-ZEORD)

I would kike to know the importance of the Field in Source List

I dont find this number specified anywherer in the Sourcelist under ME01.

The Help command states below :

Number of Source List Record

Alphanumeric key uniquely identifying the document.

This counter is assigned internally by the system at material master plant segment level.

But still I could not understand where its available in the Material Master nor the purpose of this number specified.

Could anyone enlight me on this point please ?