Short version: He didn't fuel Raikkonen's car up enough which forced an early pit stop in the second-to-last lap of the race. However at the end of the race they placed the same as they had planned, and they had for the laps before the pit stop the advantage of having a stress-free race due to being in pole position.

And the lesson he learned from that: Don't stick to the rules too closely, but also try to see if breaking some rules can have positive side effects. Experiment.

Not a fun read. Very badly written as he constantly leaves out the consequences and details of decisions and circumstances, or only mentions them paragraphs later.