Slate Geometry coordinates incorrect or misunderstood

I’m not really doing anything with the slots themselves. Essentially, I’m trying to line up the widget with the grid, SInventoryDisplay, with the border, but for now treating the grid as a widget/border as well.

I doubt it’s an issue with padding though. If it was, the white border would be off by a few pixels, not a few hundred. At least that’s what I assume, I could be wrong.