User blog comment:FairyRaven/Fairy Tail Chapter 465: 400 Years, Review and Commentary/@comment-196.217.88.80-20151207124857/@comment-4829046-20151207151750

That's debatable since Freed's runes still took it as 80+. The previous theory was that the runes detected the ages of the Dragons, but now it fits for the actual DS, besides just Natsu.