Does this graphic image help clarify your terminology?
S2000 Aerodynamics
https://robrobinette.com/S2000Aerodynamics.htm
Quote:
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Note how the high pressure (red) bubble sits on top of the splitter adding downforce. The underside of the splitter also generates low pressure (blue) and downforce but the splitter needs to be lower than about 3 inches to generate this low pressure area. Graphic by Hancha Group Consulting.
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Less blue area with a splitter, blue is lift from what I can tell - it has a negative number.
There is also an explanation for "dive planes" in that link, just more down-force and more drag.