addition is weird

Hello, i'm having a major problem, i simply have no idea what is wrong, but i do know it's not supposed to be like this here's the relevant code:

Player stats

Player[1] = [30] //Max HP
Player[2] = [10] //Max MP
Player[3] = [2] //Num HP pots
Player[4] = [2] //Num MP pots
/*
Other insignificant values
*/
Player[9]  = [30] //Current HP
Player[10] = [30] //Current MP

Faulty part of function PlayerTurn();

function Hp (e: MouseEvent) {
     if (Player[3] > 0) //Checking if player has Health potions
     {
          trace(Player[1]); //outputs to 30
          trace(Player[9]); //outputs to 30
          if (Player[1] == Player[9]) //Apparently this isn't equal, it should be but isn't. I think this may be related to the issue, but that is further down.
          {
               //OUTPUT TEXT
          }
          else 
          {
               Player[3]--; //Reducing number of health potions
               PlayerHeal = Math.round(Player[1] * 0.5); //Neccesary middle operation, i'm outputting this in a textbox later. 
               Player[9] = Player[9] + PlayerHeal; //This is were the problem lies
               /*
                 This is where the problem lies
                 you see; the answer to this is 3015
                 it SHOULD be 45 and i have no clue why.
                 if i subtract 1 then add 1 it becomes correct,
                 but i want to know why this happens.
               */

               //RECALCULATE HEALTH BAR
               //OUTPUT TEXT
          }
     }
     //OUTPUT TEXT
}

I'm still quite new in AS3, but this goes against everything I've learned, i can't really figure out what's wrong. but i do know 3030HP is wrong, when it should be 45.