What’s up with Astros’ Zack Greinke signaling his own pitches?

The Astros' Zack Greinke flashed two fingers to his catcher before Ramon Laureano launched a 449-foot home run.

source https://www.chron.com/sports/astros/article/Houston-Astros-Zack-Greinke-signal-pitches-call-As-15631989.php