How to subtract from a count

Hello, I'm making a game and I'm just a little confused onQuit event. What I'm trying to do is if a player quits the game it will message each player in the game saying '$player left the game. ($count/24)'
With the code I have I'm getting this when the player joins and quits:
'$player joined the game. (2/24)'
'$player left the game. (2/24)'
See the problem? because the player is still in the world when the message is sent its still counted as 2 when it should be 1. so I need to know how to subtract 1 from the count. this is what I have in QuitEvent:

PHP:

    public function onQuit(PlayerQuitEvent $event)
    {
        $player = $event->getPlayer();
        $level = $this->getServer()->getLevelByName($this->currentLevel);
        $levelArena = $level;
        $playersArena = $levelArena->getPlayers();
        $gamecount = count($this->getServer()->getLevelByName($this->currentLevel)->getPlayers(-1));
        foreach($playersArena as $pl)
        $pl->sendMessage(TextFormat::YELLOW . $player->getNameTag() . TextFormat::YELLOW . " left the game. (" . TextFormat::AQUA . $gamecount . TextFormat::RESET . TextFormat::AQUA . "/24" . TextFormat::YELLOW . ")");
    }
}    

 

Replace

PHP:

 $gamecount = count($this->getServer()->getLevelByName($this->currentLevel)->getPlayers(-1)); 

with

PHP:

 $gamecount = count($this->getServer()->getLevelByName($this->currentLevel)->getPlayers()) -1;