That 7 headed beast represents a literal event, not a symbolic one.
Prophesy has NEVER been a symbolic thing representing a symbolic event, NEVER.
Again, we have Daniel to use to prove this is true
Nebachadnezzar was a literal man, a king of babylon, he was not the head of a statute, or a lion with wings.
when daniel was told after 70 weeks, the city and temple was destroyed, the city and temple lay in ruins, Yet we know the fulfilment, the city and temple were rebuilt, and in 70 ad. The roman army destroyed the city and sanctuary.
It was not a symbolic event,
You interpret prophesy by taking all fulfilled prophesy as a guidline, All past prophesy was literally fulfilled. Hence all future prophesy should be also.