I don't think that OP is talking about "compensation". It seems as though he's talking about a refund. If he was "charged" two segments and flew one due to an invol. reroute, he should be credited back the one segment.

As to Original Routing Credit (ORC), he can ask. But, there's no way he gets the segment count reduced by one and gets the credit.

I would not touch this until the entire itinerary is complete. Too many things can go wrong. Once OP gets home, he can deal with this.