Here you can enter the unit cost that will be used as a standard. You must fill in the Standard Cost field if you selected Standard in the Costing Method field.
You can change the standard cost, but this will only affect new postings. If you want to change standard cost for already posted entries, you must use the revaluation journal.
If you choose a costing method other than Standard, the program grays this field and makes it non-editable.