This is a gain in the associate and so is equity accounted for. We therefore take 30% of 6/12 of 6, which gives 0.9 and is in the answer.
I think it is the realisation of half of the gain that is held in OCI. Once the subsidiary becomes an associate we would recycle any gains made. I doubt anybody in the exam got this point so I wouldn’t worry about the finer details.
Overall this question was ridiculously difficult and you’ll find that subsequent group SPLOCI questions have been more straight forward.