Pullbacks - length of a Z shape pullback Fib Target

Z Pullbacks are observed to indicate a price destination, at the exhaustion of the move, by using the Fib drawing tool. Taken from its top to bottom the resultant indication of the 2.6 Fib line gives a target price at the exhaustion of the move. Another rough estimate is to take the length of the Z and add that length twice to the top, the resultant length will be the target at exhaustion (same as 2.6 Fib).
Here we see Facebook with two Z pullbacks and the resulting Target Price is the same