Two subscriptions, Plus and Max, are under the same subscription group, with Max having a higher tier than Plus. Promotional Offers for Max are configured in Apple Store Connect. When a user subscribes to Plus and then upgrades to Max using Promotional Offers, they are prompted with "Upgrade upon expiration" (Figure 1); if they don't use Promotional Offers, they are prompted to "Upgrade immediately" (Figure 2). Question 1: What is the situation with the "upgrade upon expiration" message in Figure 1? Is upgrading using Promotional Offers special? I couldn't find any relevant explanation in Apple's technical documentation. Question 2: Figure 1 shows an "upgrade upon expiration," but after subscribing, the webhook still shows the subscription start time as the current time, meaning the upgrade hasn't started immediately. Is the message incorrect?