The width of dashboard did not change

Hello,I tried to change the width of dashboard but it did not work.
I set it like this...

This is the page of issue.
https://russellshilpa.com/my-page.html

I set it like ..sidebar-a,main body,sidebar-b

I set the width size as this page
https://russellshilpa.com/frontpage/categories/listings/10-spot.html

so, the issue page must be the same width size but it was not.
Please help me to solve this issue,thanks.