You should be checking channel name as well.

Code:
on *:text:*just subscribed*:#CHANNELNAME: { 
  if  ($chan == #CHANNELNAME && ($nick == twitchnotify) { 
    inc -u120 %spam.sub [ $+ [ $nick ] ]
    if (%spam.sub [ $+ [ $nick ] ] == 2) {
      msg $chan   DOUBLE SUB HYPE!!!! $1 just subbed!!   
    }
    elseif (%spam.sub [ $+ [ $nick ] ] == 3) {
      msg $chan   TRIPLE SUB!!!! SUB TRAIN!!!! CHOO CHOO ~ $1 just subbed!!   
    }
    elseif (%spam.sub [ $+ [ $nick ] ] == 4) {
      msg $chan   THE QUADDDD!! Kreygasm ~ $1 just subbed!!   
    }
    elseif (%spam.sub [ $+ [ $nick ] ] == 5) {
      msg $chan   PENTASUBBB!!!! DAT SUB TRAIINN CHOO CHOO ~ $1 just subbed!!   
    }
    elseif (%spam.sub [ $+ [ $nick ] ] == 6) {
      msg $chan   6 SUBS! Dat Sub Train Kreygasm ~ $1 just subbed!!   
    }
    elseif (%spam.sub [ $+ [ $nick ] ] == 7) {
      msg $chan   7 SUBS! GOGOGOGOGO!!! Kreygasm ~ $1 just subbed!!   
    }
    elseif (%spam.sub [ $+ [ $nick ] ] == 8) {
      msg $chan   8 SUBS! GOGOGOGOGO!!! Kreygasm ~ $1 just subbed!!   
    }
    elseif (%spam.sub [ $+ [ $nick ] ] == 9) {
      msg $chan   9 SUBS! OMGWTF Kreygasm ~ $1 just subbed!!   
    }
    elseif (%spam.sub [ $+ [ $nick ] ] == 10) {
      msg $chan   10 SUBS!!!!! Sub Train has reached it's destination!!!! ~ $1 just subbed!!   
      set %spam.sub 0
    }
    else {
      var %item = $rand(1,5)
      if (%item == 1) msg $chan   $1 subscribed!!!    $+
      if (%item == 2) msg $chan   NEW SUB: $1 $+ !!!    $+
      if (%item == 3) msg $chan   Thanks for subscribing, $1 $+ !!!    $+
      if (%item == 4) msg $chan   SUB HYPE!!! $1 just subscribed!!!    $+
      if (%item == 5) msg $chan   WELCOME $1 $+ !!!    $+
    }
  }
}

twitter @keyeslol