The tags are not counted if not used. Tags on disk or persistent memory i/o devices are not counted. Tags on Cicode i/o device are counted. A tag can be counted only once, a tag which is used on screen, trend expression and as alarm expression only counts once.
If you search for the phrase "dynamic point count" in the Citect 2018 help it will describe how the point count is achieved. It is not as simple as it was in the old days. But you can get a fair indication of what your point count will be by applying the concepts in that help file.