The KMS Client serial numbers help you only if you have a KMS Server or use Active Directory based activation. Read more about KMS in our article KMS Overview. This may not yet be translated.
Update: Now with Windows 10, Windows Server 2016, Office 2016
Update 2: Now with Windows 10 LTSB 2019, Windows Server 2019, Windows Server SAC, Office 2019
Update 3: Now with Windows Server 2022