That's why the dwarfs where helping him with his decision.

The numbers were code for emperor Nero. If you assign every letter in the alphabet a number based on the alphabetical order and add up the values for the name, you get 666. But only if you use the Greek name NERON CAESAR, in Latin, he would be NERO CAESAR, and the missing N gives you only 616. So some scribes in the western part of the empire would calculate in their head and write down 616. So we got two versions of the number going around in manuscripts from the time.