Hi Johannes Engstle !
Please check information from this KB about "Package Assignment to Package Servers" option
https://techdocs.broadcom.com/us/en/symantec-security-software/endpoint-security-and-management/it-management-suite/ITMS/Administration/Configuring-Sites-and-Site-Servers/package-service-settings-v12526716-d846e59464.html
If there is a requirement to assign this package only for appropriate Package Server or Site with package servers, then switch default option "Package Servers automatically with manual prestaging" to "Package Servers individually" or "Package Servers by Site"

Best regards,
IP.