The translation would be confirmed because all of the inscriptions meant the same thing.
Explanation:
The answer is technically in the passage; the text says, "the priests' statement could be read by Egyptians who understood Greek, as well as by those who knew only one or both of the Egyptian languages." Because the inscriptions meant the exact same thing, the statements could be read by multiple people, and the translation would be confirmed.
I hope you kind of understand what I meant...good luck on your assignment and have a wonderful day :3