WordPress SEO 1.4.6
When entering the SEO title in the "SEO Title" field, characters inside brackets are not counting towards the character count. Take the following title, for example:
In such a régime [the government of Chief Nanga in Nigeria],
That line is actually 60 characters long (take my word for it, or use this tool). However, the plugin is showing that I still have 52 characters left (out of the 70 limit).
When you remove the bracket at the end, the count returns to normal.