My LITE seems to be reading the right pressure, but it’s reading positive, not negative. Why?

Older versions of the LITE: 

The reference port of the LITE is on the front face of the display, you do not need to plumb anything for the reference port.  The high, or positive, pressure port gets plumbed to the space that you are monitoring, regardless of it being a positive space or a negative space.  With the LITE, it is always mounted in the space you are using as a reference and is always plumbed to the space you want to monitor.

In the room/Outside the room versions of the LITE (new/current version):

For this version of the LITE you have the option to select "in the room" or "outside of the room" as an option. 

This option refers to where the LITE is going to be located. Properly selecting this is important because the LITE has a port on the front face that is reading pressure and a port in the back that you plumb to your other location.   

For the "inside the room" option that means you are plumbing the back port to the reference space and the LITE will be inside the room you are monitoring.

For the "outside the room" option, that means you are plumbing the back port to the space you are looking to monitor. The LITE will be outside the room you are monitoring.