Category options creating woocommerce posts forms

I have added a category field to my woocommerce form. In Field Options–>Advance Options one finds a “Selection Type”, you can choose: Include, Exclude, Child of. Here is my point: those options don’t work at all for me: I tryed selecting each one of them, and completing the corresponding “Selection Terms” field, but my final form always shows the full list of categories.

I would like tho show only the children of a specific category.

Please help on that!. Thanks.