Or M - manipulated.
This story appears to be another reoccurrence of an old scheme that Elen goes into in her examinations of megaliths. We have old texts that are translated, a tragic fire that destroys the originals leaving only the translation now incontestable. OR alterations to make a 3 appears to be an 8, or interpretations thereof that misplace events in the historic timeline...
Shadowself, if indeed the information was encrypted, and nobody was able to make much of what it meant, then such manipulations would be unnecessary. Making these efforts to obfuscate some information found requires that a decision to hide the discovery had to have been made. The discovery being, some revelation that would otherwise be easily understood.