How to change the available quantity of a product based on a property in the WAN?

Question

PHP

I'm trying to change the available quantity of goods in the infoblock, based on the property. BUT nothing comes out. Please tell me how to do it

CModule::IncludeModule('iblock');
Cmodule::IncludeModule('catalog');
$addProps = CIBlockElement::GetList(
        Array("ID" => "ASC"),
        Array("IBLOCK_ID" => 18),
        false,
        false,
        Array(
            'ID',
            'QUANTITY',
      'PROPERTY_MIN_UPAKOVKA'
                    )
);

$upakovka = $ar_fields['PROPERTY_MIN_UPAKOVKA'];
$vupakovke = $ar_fields['QUANTITY'];
$kolvo = (int)($vupakovke / $upakovka );
 
while ($ar_fields = $addProps->Fetch()) {
        $arFields = Array(
            "PRODUCT_ID" => $ar_fields['ID'],
            "QUANTITY" => $kolvo,
        );
        CCatalogProduct::Update($PRODUCT_ID, $arFields);
}

Answer 1

Isn't that how it should be?
"QUANTITY" => $kolvo,