When there is a "j" it indicates it is for small children. The sizes would go j8 j9 j10 j11 j12 j13 and then 1 2 3 4 5 and so on. A junior 8 would be approximately a 2 years old child. Where as a size 1 is approximately for a size year old. The “J” stands for juvenile. An adult man might wear a size 8 or 9. It goes down from there to 7, 6, 5 (popular with adult ladies) to 4, 3, 2, 1 (popular with children) and after 1 it goes down to a 13J, 12J, 11J, 10J, etc. A 10J or 11J would be popular with smaller kids (kindergarten, first grade, etc.).