Another dumb question

[Chamberpains]

I have something like this. https://www.amazon.com/dp/B00SZ4QFW0/ref...FEAQ4CK7R6

It does the job fairly well. The guages aren't the best. They relax no matter how tight the system is. That's why I gave a couple psi range. High end pumps and guages will easily pull 30 in/hg and hold on a tight system. This one... meh... I run it for a 30 min to make sure the system is tight then I rerun for an additional hr to make sure its good and boiled for moisture. Then I leave it sit for at least an hour. To ensure it holds somewhere in the 27-28 in/hg range. Anything lower then I know my system isn't tight.