Quotation Item Issue

Hello everyone, i have many issues when I try to add items or delete items to quotation child table.

I have for example, 3 elements on my Items table:

Each item, has 3 as the value quantity, that makes a Total quantity of 9!
the problem is when I Delete one row from items, the total quantity doesnt update, it stays as “9” and the same problem happens with the others fields like “rate, base_rate, base_net_rate”
how can I refresh those native fields?
Thank you