I don't think it was an "if", there is speculation that the mark is reference to Nero [0]. If true this means it wasn't a guess about the future but a commentar

I don't think it was an "if", there is speculation that the mark is reference to Nero [0]. If true this means it wasn't a guess about the future but a commentary on current day events. [0] https://en.wikipedia.org/wiki/Number_of_the_beast#Nero https://en.wikipedia.org/wiki/Number_of_the_beast#Nero