Dramatic irony occurs when the audience knows more than the characters. How is Samneric' s description of the beast an example of dramatic irony?

The audience knows that the Beast is nothing more than a dead parachutist who has come from a war plane that was flying over the idland.  Samneric completely blow their description out of proportion to the point that the reader wants to say:  "Wait a minute, that is not at all what you saw."  Their imaginations are such that the Beast is a revelation of their most inward fears and their greatest nightmares which no adult is around to save them from.