User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-4531192-20130821185530/@comment-3146930-20130822204250

I think she meant 17. Anyway, people tend to confuse real time and book time (even Rick does it...multiple times). August 18th is Percy's b-day, so people may think that it is his 17th birthday today. If Percy was a real person, this would actually be his 20th birthday. Also Sayu isn't kind, or so she says.