Content Width

I'm attempting to set a custom content width on a blog post. I scrolled down to the bottom of the post, in the Page options section, I clicked on the "Content" tab, and then changed the "Content width" to "Limit" and specified a small width, like 50 px. When I save and view the post, the width is still the default, which appears to be 1128px.

I then went to the "Theme Options" under the Theme settings and went to Layout > Post > Content > Content width and tried to set it there. Nothing happened. This is using the child theme that shipped with the 1.04 release.

I do not have a link to provide because I'm running this as a local instance until the site is ready.