[Those stats are based on what is written in the manga and my own thinking
PL = Power Level]
Baby ranking :
Low-rank : 1-100 PL
Mid-rank : 101-500 PL
High-rank : 501 and above PL
Adult ranking :
Low-rank : 1-2,500 PL
Mid-rank : 2,501-5,000 PL
High-rank : 5,001 and above PL