De recognising investment

I cant understand a adjustment where an entity(aron) holds 3 % of shares in a subsidiary Fair valued at 5$ million ( designated to be F.V.T.P.L ) . The value of investment increase and the company recognised a gain of $400,000. After sometime the subsidiary was acquired by another entity(given) and as result Aron received shares in given with FV 5.5 $ million. I think it would be
Dr: new Financial asset 5.5
Cr De recognise old financial asset 5.4
Cr Profilt and lost $1m

But in kit the adjustment is
Dr New Financial asset 5.5m
Dr OCI 400k
Cr I/s 900k
Cr Old Financial asster 5.0m

Why do we take the Previous gain recognised out of OCI ?

Thanks