Pxl-test(), pxl-On(), and pxl-Off() use Y,X syntax.
Everything else (Line, Pt-On()…etc…) uses X,Y syntax based on window settings.
In Pxl commands, Y=0 is at the top of the screen and Y=62 is at the bottom. X=0 is at the left side and X=94 is at the right.
Everything else depends on Window settings.
Converting coordinates from Pt to Pxl is a pain. But if you always use certain Window Settings, you can memorize a formula.
For ZStandard:ZInteger, Pt-On(X,Y) = Pxl-On(31-Y,X+47).
Here's what your original code should be: (I think)
:Horizontal -31 // This will do the same thing but it's smaller
:If not(pxl-Test(32-A,47 // this is 1 pxl below the point; (Also, it's more optimized)
edit: ninja'd by Roguebantha :)