X box live subscription

I have paid two x box live subscriptions. I didn't realise that you could link two x boxes to one subscription until I had paid the second one.

I had real difficulties trying to get my sons fifa account to swap over which resulted in me learning to link two x boxes to one subscription. We used the main subscription that runs out first unfortunately and I have another subscription running until October.

Is there a way to utilise the remainder of that subscription that hasn't been getting used or is it easier to just renew the one that is running out and just accept the loss on the other? There is ten months left on one subscription that I would rather not
waste.

:)