Então, pelo que eu entendi do shop system, essa seria a parte que vai jogar o valor no banco de dados, correto? 
Então, aonde eu encaixaria a formula? 
  
 
		
if($buy_offer['type'] == 'pacc') {
									$player_viptime = $buy_player_account->getCustomField('viptime');		
$player_lastlogin = $buy_player_account->getCustomField('lastday');
$save_transaction = 'INSERT INTO '.$SQL->tableName('z_shop_history_pacc').' (id, to_name, to_account, from_nick, from_account, price, pacc_days, trans_state, trans_start, trans_real) VALUES (NULL, '.$SQL->quote($buy_player->getName()).', '.$SQL->quote($buy_player_account->getId()).', '.$SQL->quote($buy_from).',  '.$SQL->quote($account_logged->getId()).', '.$SQL->quote($buy_offer['points']).', '.$SQL->quote($buy_offer['days']).', \'realized\', '.$SQL->quote(time()).', '.$SQL->quote(time()).');';
									$SQL->query($save_transaction);
									$buy_player_account->setCustomField('viptime', $player_viptime+$buy_offer['days']);