Pro rata refunds query

I have 2 devices both on the Ring Basic plan which have just renewed to new annual subscriptions - obviously it would make more sense to have one Ring Standard plan cover both of these devices so it’s £79/year rather than £49x2/year. If I request to cancel does the pro rata refund cover all the time not used? Or is there some kind of cap? This renewal only happened yesterday so I don’t want to end up costing myself more money.