With a historical mode Adapty calculates metrics based on App Store Connect Sales reports. Reports are anonymous and Adapty can't match user's transactions from month to month. That's why this mode is an estimate and can vary up to 10% from real values.
Way to calculate
Subscription conversion rate
(#cancels) / (#active subs on start + #new subs + #renewals)
Average number of periods user is subscribed
Sum by all subscriptions (#sub. price * #subscribers) / (sub duration)