Hi Milli, I am sourcing my info from the course "The Wyckoff Method, How Professional Traders Think, W.H.C Bassetti, Golden Gate University, Fl 498S", which I believe was the condensed educational course in Wyckoffian technical analysis popular post 1930's.
On page 6, paragraph 2 we read "Corrections in price represent entry opportunities when other criteria are met. Normal corrections = 50% but may range from 33-66%. The traders eye should be caught to reactions of this magnitude and supply and demand study should be made."