Inset not working? Width seems always set to Full

Hello, 

I can't seem to get the section width to change to inset, or when I do, it just seems to be the same as full. This appears to be the same for all my sections, but specifically I was trying this with the navigation section. When I switch between full and inset nothing seems to move.

I'm using version 7.1 and would like to inset some sections of the web page but have some sections at full width. 

I may be wrong but I had a feeling this was working for me previously (although maybe on another project - not sure).

Grateful for any help. 

Thanks

Adam

Folks might be better able to help if you shared a link to your site so we could see the content.