My widget doesn't fill the screen like the other ones i have

I have other widgets that have been working fine but I the one i’m currently working on leaves part of it unfilled-- even though in the editor it fills the space.

But in the game it doesn’t fill all the way.

Context: I have a size box that’s the parent of the rest of the widget and I’ve been using an animation with the sb to minimize and maximize the size of the widget.