Hola Robin - I checked your test results and the question was multiple choice and had two correct answers: "Al discutir" and "Al haber discutido"

As you only gave one answer out of the possible two, the system awarded you half a mark (you need to give both correct answers to get a whole mark) but the message the system gives you is indeed rather misleading because it says "1 Nearly correct". I agree that you got one answer completely correct! I'll look into how we can change wording to avoid this kind of confusion in the future. 

All best

Shui