How to export item’s stock quantity?

Hi, I can’t get a column with item’s stock quantity on a csv file.
On Woocommerce I use Manage Stock and enter Stock Quantity manually on each item’s intevory tab.
On Product Feed Pro I have configured a custom feed /csv, and to get item’s stock quantity I have added a custom field with a custom attribute named “quantity” using the value “Quantity [Stock]” but the column doesn’t show on the resulting csv (no header, no content, no column at all).
All the other columns/attribs are fine on the csv (id, title, price, etc…)
So how can I export my product’s stock quantities to the csv file? I must be doing something wrong.
Thanks for your help!