Can Expert explain flwg lots caculation code for me ? especially why is this "500000" there ? thank you

I had tried to figure it out for several days, I need your help to explain for me flwg code , especially the ‘500000’, because I dont’ know what it is used for ? and for me it should not be there. but anyway, here is the code:

//±-----------------------------------------------------------------+
//| Calculate position volume |
//±-----------------------------------------------------------------+
double Lots()
{
double maximumRisk=0.1;
int lotsDigits=MathLog10(MarketInfo(“EURUSD”,MODE_MINLOT)); // I deleted " (int)- "
double lots=NormalizeDouble(AccountFreeMargin()*maximumRisk/(500000.0/AccountLeverage()),lotsDigits);
if(lots>MarketInfo(“EURUSD”,MODE_MAXLOT))
lots=MarketInfo(“EURUSD”,MODE_MAXLOT);
if(lots<MarketInfo(“EURUSD”,MODE_MINLOT))
lots=MarketInfo(“EURUSD”,MODE_MINLOT);
return(lots);
}