negative integer in vacuum field?

[89S10_Project]

Folks-

I am seeing an occasional negative integer in my datalog under the Vacuum field.

It seems to me that the 17 I am seeing in that field at idle indicates 17 pounds of vacuum. IE, the opposite of pressure.

Carrying that out to what seems a logical conclusion, when I floor it and I'm seeing -3 in that field... this would mean 3 pounds of pressure (in other words, above atmospheric pressure).

Just making sure I understand this properly before proceeding further.

Vehicle is an 89 S10 Blazer with a GenII smallblock, 5.7L TBI engine. I ran the numbers and it's a 94 crate engine, so it was clearly replaced in the 89 C1500 I pulled it out of.

EDIT: Correction! It's a Gen1 smallblock, 1994 crate engine, TBI 5.7, all else being as above. Thanks to Tom for educating me!