Banana (Sep 2018)

Hi,
I am referring to Banana (Sep 2018) problem, more specifically, Question 3.
Question can be found here: https://www.accaglobal.com/content/dam/acca/global/PDF-students/acca/SBR/sbrint-2018-sep-q.pdf
Answer is here: https://www.accaglobal.com/content/dam/acca/global/PDF-students/acca/p2/exampapers/int/p2int-2018-sep-a.pdf

In Q3, they say that the bond should continue to be recognised at amortised cost. I just don’t understand the following: “The third party is obliged to pay additional cash to Banana should bond values rise. Banana will also compensate the third party for any devaluation of the bonds.” Since the answer says that the Bond will continue to recognise the bond at AC, how this gain/loss on changes in the fair value of the bond should be accounted for? Gain/loss will be “independent” from the bond and will not affect Balance Sheet?

Thanks,
Giga