serverOptions: showAllDiscs=true (full license)

[simoncn]

When you load a UPnP library into JRiver, JRiver uses UPnP Search operations to do the loading. The DiscNumber tag is not part of the UPnP standard metadata that is returned by a UPnP Search operation and this is why you are not seeing Disc # tags in your JRiver library.

You can solve this by copying the library files to the machine running JRiver and loading the files into JRiver from the local copy.