PROD_PORT_ID and PORT_VALID_PROD_ID in S_QUOTE_ITEM

I'm importing Quote Item via EIM, and for a bundle product i can see at the table S_QUOTE_ITEM that PORT_VALID_PROD_ID and PROD_PORT_ID not null for the subitem, but in EIM i can's see any mapped columns to import those fields are these columns needed o they can be left with null.

and in teh same they have some id but i don't know where it comes from, at the table S_QUOTE_ITEM it shows they are foreign keys to S_PROD_ITEM, but if I query that table is empty

Any ideas?