That is, a guess at the amount of data one facility of a modern signals intelligence agency (belonging to a super-power) is being compared to the amount of record keeping space a cold war era security agency (belonging to a Soviet client-state) possessed. The two agencies have vastly different missions (state security versus signals intelligence), operated at vastly different scales, and in completely different eras. The two facilities being compared are not at all similar. A large computing facility (probably processing raw data) is being compared to a large library archive (largely storing files and documents generated by the agency).
No valid conclusions could possibly be drawn from this comparison. The closest we could come to a valid conclusion is; if we printed out 5 zettabytes of data we would have wasted a lot of paper.
Edit: What I'm trying to say is that this is an apple to oranges comparison made across space and time.