A bit late but just in case anyone else wonders: u15dvdinfo lists her 2007 release as 小5. 小5 doesn't mean 5 years old, it means 5th year of elementary school, in other words 10-11 years old.
Likewise 中1-3 would be year 1-3 of middle school and 高1-3 would be year 1-3 of high school etc.
So the...