How to perfectly have GUI position accordingly to screen size no mater the size correctly? [Edited[

Ok so I know how to use scale to position GUI's but it does not want to go to the full position for screen more then 1600x900 how can I fix this?

Here's where it is now, This is on the edge of my window where the explorer is.

Here is where the problem is... As you can see when the explorer is gone it doesn't fully go to the edge How can I fix this so it does without losing the position in the first picture?

And the toolbox and explorer is at max size so it can't go any further.

Size and Positions of the main GUI's in ScreenGUI

List: (Main Frame)

--Size: {0, 202},{0, 300} --Position: {0.814, 0},{0, 28}

Close: (Text Button)

--Size: {0, 186},{0, 24} --Position: {0.811, 8},{0, 297}

Title: (Text Label)

--Size: {0, 200},{0, 24} --Position: {0.815, 0},{0, 3}