In engineering parlance to the vacuum world, inches generally means Hg, Hg is the periodic symbol for mercury. Bizzabolla may have just posted in shorthand. If it were in pounds per square inch (psi), it would have to be in psiA (Absolute, that is, 0 psi plus 14.7 (standard atmospheric pressure at sea level)). Why? Well, the most common is psiG(gage) which automatically compensates for the barometer. And, psi units are double the size of inches of mercury so you have a large gage “swing” on the needle so accuracy is higher.
These psia gages are pretty specialized and your normal “mity mite” hand pump’s gage is in inches of mercury/inHg/”Hg much more common! 5”Hg for 15 mins. has proven to be optimal vacuum for me, unwrapped. See the threads for condom pumping, intriguing!
Now, I’m getting hard in the tube, releasing vac. then wrapping junior’s head and glans, I’m circumcised, with the ther-a-band. My peak I’m using now is 7-8”Hg for 15 mins with no doughnut around my glans.
I use a hang/pump combo that suits my schedule.
The units will be written on the face of the gage. If it is a dual scale, inner and outer, the legend will be ordered consistently with the scale. They may even be color coded.
Have fun!
j