Positive /neg field in VTAA

Dear sd experts plz let me know one doubt plz

i know how to create so many quotations from single inquiry number  ,, simple in copy control vtaa --- positive /negative field we will keep blank

so if we do like this we can achieve .

but in OR TO DEL also vtlf at item level postive /neg field is there .. i am asking this purpose is also same like vtaa ?

if so what is the use of creating so many delivery's from single sales order no bz schedule line dates are different

thanks a lot