Thanks for your question. If you're referring to the term "Unit 19", "Unit 12", etc., then the term is referring to a geographical area. In Prescott Valley, the zoning code R2 is used to designate multiple unit housing.
So for example, if you're looking to invest in a tri-plex, look for the zoning code R2. If you're doing the opposite and are eliminating the R2 zoning from your searches, let me know and I can have all the properties delivered to your inbox automatically each day.
Hope this helps.