Looking at https://musicbrainz.org/release/f3ebe130-3be3-4615-b917-9e5b30b884c9 it appears that two releases have been merged, but instead of merging the discs, it appears they have added the medium from one release to the medium for the second.
Is it possible to merge these two mediums?
Not that I know - but since they use the same recordings I don’t think you lose anything if you just delete one 
If you delete the first CD, you will keep the 9 current disc IDs.
If you delete the second CD, you will lose 8 disc IDs.
A release with 9 disc IDs does not mean much, is not very specific.
But maybe it is better to keep them, as they do not appear on any other MB releases.