If you selected Standard in the Nacin vrednotenja field, the program uses the contents of this field to complete  the Strošek enote field, and the only  way that you can change Unit Cost is by changing Standard Cost.
Če v polju Način vrednotenja izberete Stalni, program z vsebino tega polja zaključi polje Strošek enote, polje Strošek enote pa spremenite le, če spremenite polje Stalni strošek.