I recommend using UIListLayout with wrap and flex features enabled as it would better fit the grids in your frame. You can set the Y size of your elements to be 100% the height of your main frame and by having a UIListLayout with it’s direction set to horizontal and the “Wrap” property set to true.
Yeah, the negative padding doesn’t make sense.
And the different sizes are a mismatch between the desired frame size coming from the UIGridListLayout and the UIAspectRatioConstraint inside the frames themselves.
If anything you should have the AspectRatioConstraint on the parent frame and then let the grid items themselves just be controlled by the UIGridLayout.