Well, I've figured this out finally, not easy when you begin on using Odoo, this field is related to the following configuration inside :
Sales -> Configuration and under Delivery (or Shipping) where you choose between No Cost or Authorize shipping costs
if you select No Shipping Cost, you will get the right listing, if not, I guess you must add some cost for each country somewhere on Odoo, for now I just select No Shipping cost and it works.
Later I will add a comment to tell you how to add those shipping costs / country.
Cheers !