Retrieving Issued Floating License Leases with JAVA API - Example?

I tried to retrieve the used licenses for our JTS license server with the Java API.

After studying the API doc, we found that this should work with the ILicenseAdminService2 interface.

In principle the tool is working (so we can connect, ask from the license types, but this is an  ILicenseAdminService).

ILicenseAdminService2 licenseService = (ILicenseAdminService2) ((TeamRepository)repository).getServiceInterface(ILicenseAdminService2.class);
IContributorLicenseType[] licenseTypes = licenseService.getLicenseTypes();

Then we tried the function

UsedLicenseInfoDTO used = licenseService.getUsedLicenseInfo();

But it seems, that we only get an empty DTO

com.ibm.team.repository.common.model.impl.UsedLicenseInfoDTOImpl@f44031 (internalId: <unset>) (totalUsedCount: 0, countedActiveLeases: 0)

In another post there was mentioned another DTO (LicenseLeaseDTO) but I found no other information about this DTO

Does anyone know, if we missed something (or using wrong interfaces)? Or is there a documentation about this?