Untested

on *:TEXT:&guess & &:#ninja_matt: {
  if ($$2 !isnum 2-) || ($$3 !isnum 2-) msg # Only numbers higher than one please.
  else {
    var %num $int($$2), %range $int($$3)
    if (%num == $r(2,%range)) {
      msg # You guessed correct! You just gained %num points!
      inc %guess [ $+ [ $nick ] ] %num
    }
    else {
      msg # Oops. You guessed wrong, the correct answer was $v2 $+ . You just lost 1 point.
      dec %guess [ $+ [ $nick ] ]
    }
    msg # Your score is now %guess [ $+ [ $nick ] ]
  }
}