That’s very weird. The site very poorly explains it’s 20%. Also checked a couple of recent bookings and they all say 20%.
It could be one of two things I suspect:
1. AI as usual badly f-ed up. In which case you would get nothing from them. Not even an admission of any kind.
2. Do you have elite status with AI and the person’s ticket you cancelled doesn’t have elite status or that status was not reflecting in the booking? So when AI first introduced cancellation fees for awards they exempted elites from this fee. When they realised that it was elites who were responsible for the bulk of award cancellations they changed the rules and elites also had to pay the cancellation fee. Now I haven’t been TMC for years now but IIRC - the cancellation fee was the same for elites and muggles. But they could have changed the rule to lower the cancellation fee for elites - though I never heard that they did. But that could be a possible explanation for this.
Either ways I wouldn’t hold my breath for AI to payout the balance 10%, I’m sure you’re very familiar dealing with them as it is. Good luck.