Are you seeing this "First Class - Fare class O" on CO.com? If so, then it's most likely just a bug on the website.

To go back to basics - what do you think you have bought? Did you buy a first class fare? According to this page COPA O class is an economy fare class.

If the only place you're seeing this "first class" thing is CO.com when viewing the itinerary, then it's a mistake and you are in economy.