I need to check my guide thread and stuff and see if I have a typo with this somewhere.... Wouldn't be the first time even though I try to proof read everything. Absolutely -0,5 inHg. I keep mentioning -0,2bar also because that is the closest reading on Noogle gauge, its not spot on the same but very close. Keeping things a nothc or two below this is likely the safest approach and it still does the job.