How to determine the number of unique customers and regular customers?

Question

Marketing

It is not clear how to calculate, since for each category of goods there is an owl time period for sale

Answer 1

To be considered unique, they need to be marked somehow. Ideally, do not provide them with services and goods without registration (although this is a minus for business, obviously). Try to track anonymization attempts by compiling some kind of "digital fingerprints" of people (coincidence of fingerprints will mean that this is the same person). In any case, the figure will be approximate. Not approximately - only according to the passport.
To calculate the constants - yes, you will have to determine your own reasonable time interval for each product. Alas, there is no other way. Some goods are bought only once in a lifetime, so it makes no sense for them to be permanent at all.

Answer 2

upd:
@uranus235 I repeat, everything works. I was not too lazy and wrote a gif
https://www.dropbox.com/s/9n44lszojcoc9ck/gif.gif.gif
See what errors are in the console, or throw a link to the site.