Layout position

Hi
I have taken over a site from someone else (no longer available) and I am struggling to make changes to the site.

I have found the content item that I need to change (if I unpublish it the text I need to alter disappears) but within the content item the body section is blank. Under the body text input block is a list of tick boxes called LAYOUT POSITION.

I have no idea where to alter these layout positions. I cannot see them in the theme folder.

I am stumped.

Can anyone advise me please?
Libby

I can see this is a custom content type with layout position as field for the feature content type but I can't find where these fields are defined.