Everything like frames, text labels, text buttons, text boxes, image labels etc…, ensure they all use scale and no offset which is the second argument in UDim2 pairs.
So basically, on X, change Scale to 4 and offset to 0. On Y, change Scale to 1 and offset to 0.
I know. I am saying to change the scale property on the x axis to use 4, and the offset property on the x axis to use 0, and the scale property on the y axis to use 1 and the offset property on the y axis to use 0.
What @7z99 says is that everything must be in Scale, make the Gui return to its initial size and use this plugin, select all the descendants of the Gui and in the window that will open the plugin press Scale, then change the size of the Gui to Scale too.