In the beginning of Half-Blood Prince Dumbledore assures Harry that no one besides the two of them is aware of the entirety of the prophecy:
"There are only two people in the whole world who know the full contents of the prophecy made about you and Lord Voldemort, and they are both standing in this smelly, spidery broom shed.
However, at the end of Order of the Phoenix Dumbledore tells Harry:
"The official record was relabeled after Voldemort's attack on you as a child," said Dumbledore. "It seemed plain to the keeper of the Hall of Prophecy that Voldemort could only have tried to kill you because he knew you to be the one to whom Sibyll was referring."
This makes it seem like the keeper had also heard the full contents of the prophecy. If he had only heard part of it, why not just listen to the rest instead of relying on Voldemort's interpretation? If the answer to that is that a prophecy cannot be listened to without being destroyed, then how was he able to label it in the first place? If the labels are somehow automatically generated by magic, the keeper would surely not be audacious enough to relabel it based solely on Voldemort's interpretation, especially as he would have no way of knowing that Voldemort had ever heard the prophecy.
So, if we assume that the keeper had in fact heard the entire prophecy, how do we account for Dumbledore's assertion in Half-Blood Prince? Did Dumbledore simply misspeak? Or was the keeper no longer alive, so technically no one currently knew the contents even though someone had known the contents?