Right margin in Gantt chart can't be made smaller than 1.14

I have several projects that won't allow the right margin of the Gantt chart to be made smaller than 1.14. This occurs when I set the paper size for anything above 11 X 17. I copied an 11 X 17 layout that had a 0.5 margin, and then change the paper size to C-size and the right margin changed to 1.14, and it can't be made smaller; it can however be made larger. All other margins stay the same and can be made smaller or larger. (See the attached screen shots of the margin setting from the 11 X 17