WordPress at a glance
filter is not described

woocommerce_order_item_quantity filter-hook . WC 1.0

Usage

add_filter( 'woocommerce_order_item_quantity', 'filter_function_name_5646', 10, 3 );
function filter_function_name_5646( $item_quantity, $order, $item ){
	// filter...

	return $item_quantity;
}
$item_quantity
-
$order
-
$item
-

Where the hook is called

wc_reduce_stock_levels()
woocommerce_order_item_quantity
woocommerce/includes/wc-stock-functions.php 173
$qty       = apply_filters( 'woocommerce_order_item_quantity', $item->get_quantity(), $order, $item );

Where the hook is used (in WC core)

Usage not found!