It is on the Title Page of a document that dates to the 5th Century AD.
John didn't write it. Nobody knows who put it there.
Probably some 5th Century St. Scofield malcontent.
The Syriac Vulgate is dated kindly about 400 and later than that if one is being strict, up to the 500’s.
In short, any heading in it was very late, and was no different than the heading in any of our current bibles....an addition by an editor/scribe.
In this case it’s entirely in keeping with the scholarship that says early Christianity held to a late date of Revelation and that that did not change until much later....400-600 being much later.
There is no logical explanation for Christian writers continuing to look to the future for the fulfillment of Revelation events if such things had already taken place. And the ante-nicean fathers never mention such things except as future events.
Ooops....The Apostles forgot to mention to anyone that everything was fulfilled. How careless of them!
Gimmeabreak!