Not sure how you got in that state as that image should only be 32 units high in the UI screen.
The margins look odd though and I’m not sure the behaviour is what you want. The User Manual covers each attribute pretty well: https://developer.playcanvas.com/en/user-manual/user-interface/elements/
In the image on the left where the button is a small square, you have the element size as Width 32 and Height 32. That is not the case for sample project you posted. On that project the Width is 32 and the Height it -328 and you have the left side anchor set to 0.5 for some reason. I forked your project, set the Height to 32 and set the anchor to 0 and now have a nice white square.
Combining the offset, negative sizing, and scale blending to 0.5 all have their effects. I suggest changing only one item at a time and experimenting with the various effects. Then maybe change two things to see how they interact.
Thx for your reply:)I will read it.
Thx:)I will try it again