Back to the maths channel issue though, there really is enough information available, if you have the inclination to look & have a mess about.
For instance, if you look at the link that Liteace included, there is a psdata file that is available to download. This psdata file includes the relevant "RPM / frequency" maths channel, which (as has been mentioned) it is possible to export & then import into your own maths channel collection. There really is no need for any specialised knowledge in order to make this work.
I will go on record here & state that I too struggle with these maths channel formulae (I am not a natural mathematician), but Pico do give us "thicko's" a leg up I think.
I should also add that, I do wish that Pico would try to avoid making things like this, so cryptic. Most mechanics / technicians that I know, are not rocket scientists & these useful functions should be made available to us, without the drama (see my Pico feature request post https://www.picoauto.com/support/topic14691.html
Good evening gentlemen.