Page Title Format Not Working with Prefix

So I set the page title format on Site Manager -> Settings -> Content to

{%pagetitle_orelse_name%} - {%prefix%}

I do want my prefix at the end of the title. I have also set the Page Title prefix to our site name.

My understanding is that this should append the site name (prefix) to the end of the page title regardless of whether I set the page title in the meta-data section of the document or leave it blank (which should use the name of the document.)

However, the prefix doesn't get appended. It is just using the page title defined in the document's meta-data properties (where I don't include the prefix).

So example, I expected the page title to read "Example Title Tag - Site Name" instead, it just reads "Example Title Tag"

What am I doing wrong?

Thanks, Sharon