The question was :
How much of wave [B] needs to correct wave [A] in an ABC correction?
For non Elliotticians that probably means nothing.
An ABC correction is simply some sort of 3 wave move like Fig.1
Wave [B] must correct some part of wave [A], as if it don't correct any part of wave [A], then it cant be labeled a correction.
Wave [B] corrects some part of wave [A] before continuing in wave [C].
The key point is the end point of wave [B] MUST be inside the length of wave [A]
The normal retracement is around 50-61.8% of wave [A], but it can vary and there is no set limit, but it MUST move into the wave territory of wave A like as shown in Fig.2 & Fig.3
Fig.2 is a simple Zig Zag, but note that wave [B] enters into the territory of wave [A], that is a MUST
Fig.3 is a triangle for wave [B], but the end point to a triangle is at wave E, so as long as wave E is inside the length of wave [A] then its valid in the case of a triangle.
Fig.4 is incorrectly labeled
At 1st glance you can see that some part of the triangle is inside the wave [A], but if you look closer, the end point of wave [B] is outside the length of wave [A], so it can not be labeled like so.
Fig.5 is correct, the end point to wave [B] is inside the length of wave [A].