by "Documents" we mean the information of pages, pictures, files, etc, that where indexed. Sometimes we use 'URLs' as synonym for that
By "DHT Words" we mean database-entrys of (hashed) words from Documents an where to find them in the documents-database. That why it also called RWI (reverse word index).
Counting these values is just an information for people, looking at them
The more documents you have - the more entrys could be found on your local-machine.
The dht-words are primary used to be distributed in the p2p-network in order to concentrate documents for words on machines in the network.
YaCy is robust against deleting the one ore other, but deleted dht-words can't be distributed and deleted documents can't be found or distributed.
Since we switched to store documents in solr every document can also be found - even if there is no dht-word pointing at them.
If you delete things for a domain you delete the documents for a domain.
If you deleted all domains your index shoud be very smal now
The delete-options for words may be a little outdated. If your realy whant to delete a word it is ok to do it without any options.
If you also whant delete the documents for a word use that option.