I am new to mold making, and I am trying to figure out what is meant by Negative vs. Positive draft angles.

I understand that the part needs to be drafted to more easily pop out of the mold. I found this explanation from Solidworks:

2010 SOLIDWORKS Help - Draft Analysis Overview

From this site, I understand that defining a part's face as having a positive or negative draft is based upon the reference angle, but I really don't understand what this reference angle is in "reference" to. My guess is the pull direction somehow, but don't understand why the upper cope of the mold wouldn't just be pulled straight up at a 0 deg reference angle (if this is what that means).

I created a part file to create an example and attached it here. I just picked the front plane as the reference split plane, and the pull direction is normal to this. I am just using the default green, yellow, red color-coding for Draft Evaluation.

In the part, the angles are all 15 degrees, and the flat sides have no draft. If someone could please explain to be the actual meaning behind the relationship between the positive and negative part angles and the reference angle, I'd appreciate it.

I think I am partially confused because other sites have images such as these:

Thank you!!