Parallel channel's upside shows the area where wave Y is equal to wave W.
It will be the minimum target around $18k. It perfectly coincides with the 78.6% level.
Correction also could make the full retracement to the previous major top around $20k.
I highlighted the target area of possible wave Y development with orange .
After that we could see another drop within a second leg of correction in bitcoin .
The target for that move down should be recalculated once the wave Y is done.