Impairment of goodwill – foreign subsidiary

Hello,
My question relates to Impairment of goodwill – foreign subsidiary. In the revision lectures of Mar/Jun 2020 – question Hummings Co, you mention that Impariment loss could be retlanslated using either CR or AR. So it doesnt matter which one will be chosen? I did my calculation prior watching the lecture and I used the AR and the SFP was not balancing.
Thanks!