Visual Studio 2017's "Find Shelvesets" TFS command displays:
Results (showing 100 of 392)
How do I access the other 292 items?
Either use the commandline to list them all:
tf vc shelvesets
And
tf vc shelve /delete
to delete one.
Or download the TFS Sidekicks which provides a dedicated UI for a number of clean-up actions, including old shelvesets.