UPDATE: The MLS Discipline Committee's release came out on Friday without Castillo's name to it. This is due to an appeal by Castillo and the MLS Player's Union. The following was confirmed by a league official: "Castillo and the Players Union have appealed the DC's decision on Castillo and thus we will not know the outcome until next week. Castillo was already suspended for this week's game due to the red card, which allowed for the late appeal."
In total four games for his outburst two weeks ago following the 2-2 draw against the Portland Timbers. Following that game Castillo was seen yelling at the sideline official, verbally abusing him as some would call it. Several FCD players had to restrain him and pull him towards the locker room.
This suspension length isn't at all surprising. The league loves to make examples of players who do this sort of thing. We all may remember when Brek Shea was suspended a set of games a couple seasons ago for kicking a ball at a sideline official.
The one saving grace FCD does have in July is the USOC run and the friendly against Aston Villa. Castillo will be able to stay in those games, which the club needs to have in order to keep him fresh.