$lines isn't the right way to do it.
//say $ini(tanklinplayers.ini,players,0)
$lines is counting the [topic] line as well and is why you got 1 more thanthere are users
you may want to use the ini to do more later and as other data is stored in it $lines would be increasing while the actual user count may not.
also, i need a message that say: you aren't registered if user try to unregister when not in the list
take some time to look at the code and read the help file.
/help $readini