This is one of the counts I've been tracking on SPX since the summer, and updating in real-time since November. The premise is that P.3 topped in January, and the subsequent run-up was a big (B) wave forming an expanded flat with the higher high in September, followed by a nasty 2.382 drop which we're in now.
While 2.382 is larger than most typical corrective waves, we have precedent for this at the larger scale -- the 2011 correction. And in this case it would bring us to the level of the 2015 highs, which is an ideal target for P.4.
There are two ways to count the initial 1-2/i-ii of C, but both have roughly the same targets. So I'm going with the count that has a better-looking wave 3. Not much else to add, so far this is playing perfect Fibonacci Pinball.