JugglingReferee wroteWe were instructed to report the warning like a foul, and have the scorer write down the player's number, and the quarter and time of the warning.
Report this from the reporting area.
Also, be careful about "reporting" numbers for anything except a foul, and a charged timeout. No numbers for delay of game warnings, three seconds, free throw violations, etc. Some half-interested, half-distracted, scorekeepers might mark it in the book as a personal, and team foul.