p2 june 2013 question 1 note 1

hi can someone plz help me on 1 june 2011 trailer aquired 14% of caller. but as at the 1 june 2011 it did not have significant control. but as at 1 june 2012 it had significant control. so the value of the 14% was 280. so there was a gain of 20. this gain is suppose to go in the retained earnings right? at the year end 31 may 2013 the 14% holding was worth 250. it has increased by 30. so how do i account for that????? in the marking scheme it says minus the reversal of investment 30 can someone plz explain to me how that 30 reversal was calculated.