As a developer I have a question I would like cleared up. We offer two tiers of annual subscriptions in our apps. These subscriptions are under the same subscription group in App Store connect. My question is, if a user purchases tier 1 of the annual subscription for $10.00, and uses it for 6 months; then chooses to upgrade to tier 2 which costs $20.00 per year. Would the user be pro-rated the difference in price i.e. charge only another $10.00 at the time of the upgrade., or are they charged $20.00 and then refunded the difference in their remaining lower tier subscription? I keep finding inconsistent answers across the Apple community forums on this.