Serbian term (edited): ročnost robe // preostali rok trajanja robe

from the context it's clear that:

ročnost robe = preostali rok trajanja robe

IOW how many days are left before the sell-by-date .

Ročnost Robe po svakom artiklu na dan kada je Roba otpremljena sa skladišta Prodavca mora biti najmanje 80 % roka trajanja koji je određen na Robi
=>
if the sell-by-date for an articled is fixed at 100 days after production/packaging, then these goods can not be delivered from the warehouse to the Buyer is there's is less than 80 days left to the sell-by-date.

Can't see any way to make it just one word.