First I will actually answer your question.

For West slow cure epoxy at 70-85F

For small projects using thin layups, roughly 120 gram/m2 of carbon and glass. I set the cutoff on my Gast pump at 20-24 in of Hg as marked on my gauge.

For large layups, I normally adjust the pump to give me 10-15 in of Hg at the mold.

If it really important or I have the time, I pump the setup down with dry cloth as a test. This gives my some practice, checks for screw-ups and lets me see how the cloth lays. A couple of times I found big wrinkles.

Theory and FYI

From what I know on the subject, the resin supplier gives you minimum pressures for a temperature range. If you go below that you can have problems. It has been years but I remember the experts talking about wicking, wetting, boiling and viscosity.

The pressures the resin suppliers give you are normally at the mold.

A lot of what you see and hear on the internet is what someone knows works for them. It is specific to their methods and setups