no, you can't have - there, in PHP that means $days - 2selected (minus).
You'll need a bit more "serious" hacking in there -- create a new $xxxselected variable and do some if's. Same as $defaultselected, just say $lastvisitselected.
It means adding it to functions.php as well, if I remember correctly.
If I need to do all that for you, I might as well write the hack

-- just look around at how $defaultselected behaves and create a new variable