PERM date of completion of relevant studies

On the PERM they ask "year relevant education was completed". By that date do they mean the date someone completed their degree and became eligible for it? or the date the diploma itself was awarded? (At times the award ceremony is 6-12 months after the degree is completed and can be a different year).

Does it even matter what was checked out in the box of the PERM? or the only thing that counts is the diploma and the evaluation of it?