Incorrect EXP gain displayed

[Samurai Legend]

Hello, I am a bit confused in what I did wrong in one of my scripts. So in the Gym I allow it to show how much EXP it gains. However, it shows a different amount from how much it actually gain.

Generate gains -

$gain +=rand(1,3) / rand(800,1000) * rand(800,1000) * (($row['will'] + 50) / 300);

    $row['exp_needed'] =
           (int) (($row['level'] + 1) * ($row['level'] + 1)
                   * ($row['level'] + 1) * 2.2);

       $expgain = $gain;         
       $expperc = ($expgain / $row['exp_needed'] * 100);

 

Update users EXP -

$db->query("UPDATE `users` SET `exp` = `exp` + ({$gain} / 10) WHERE `userid` = ". $_SESSION['userid'] ."");

 

I don't see where I went wrong.

[KyleMassacre]

What would you like to update it as?

Here is some dummy code I ran in phpfiddle:

<?php 
$gain = 0; 
$row['will'] = 100; 
$row['level'] = 5; 
$gain +=rand(1,3) / rand(800,1000) * rand(800,1000) * (($row['will'] + 50) / 300); 
$row['exp_needed'] = (int) (($row['level'] + 1) * ($row['level'] + 1) * ($row['level'] + 1) * 2.2); 
$expgain = $gain; 
$expperc = ($expgain / $row['exp_needed'] * 100); 
echo "Gain: ".$gain."<br/>Gain / 10: ".($gain/10)."<br/>Exp %: ".$expperc; 
?>

And here is the response it gave:

Gain: 0.502012072435

Gain / 10: 0.0502012072435

Exp %: 0.105686752091