If you just want to change the way it shows up on the page, but not the actual title, you will have to edit bfa_header_config.php.
If you want to change it in the logo area - In 3.5.3 look at line 202
HTML Code:
bloginfo('url'); echo '/">'; bloginfo('name'); echo '</a></h' . $bfa_ata['h_blogtitle'] . '>';
and change it to
HTML Code:
bloginfo('url'); echo '/">'; bloginfo('name'); echo 'YOUR EXTRA INFO GOES HERE</a></h' . $bfa_ata['h_blogtitle'] . '>';
If you want to change the title that overlays the header image, in 3.5.3 look at line 340
HTML Code:
bloginfo('name'); echo '</a></h' . $bfa_ata['h_blogtitle'] . '>';
and change it to
HTML Code:
bloginfo('name'); echo 'YOUR EXTRA INFO GOES HERE</a></h' . $bfa_ata['h_blogtitle'] . '>';
and change it to