Sales Invoice Fields issue

Hi Guys
I am having an issue in a custom doctype similiar to Sales Invoice, i have a child doctype same like Sales Invoice… child doctype-> “Sales Invoice Item”

when i delete any row of “Sales Invoice Item” there are two fields below that table Processing Fee and Ew Cost these two fields are clearing up automatically and also a field above the table it also clears when i delete the row of child table…

Even when i inspect the fields there are values of those fields… Any help will be highly appreciatable.