You can't just increment a number in a file like that. You have to first read in the current number, then increment it and write back the incremented number.

Code:
  var %value = $readini(blah.ini,$nick,lines)
  inc %value
  writeini -n blah.ini $nick lines %value


Now, you can of course increment the value right in the var line or in the writeini line. This just breaks it down so you can see the process.