To view your churn rate using the exports, we recommend pulling the Subscriptions export (Status: all, Time range: All time). To clarify the definition of % Churn = Total subscriptions churned over the selected interval / total subscriptions active at the BEGINNING of the selected interval.
Once downloaded, you'll go to the activated_at column and remove all subscriptions that were activated after the time period you are analyzing. For example, if you're checking your churn rate for January 2020, you'd remove all subscriptions that were activated after January 1st, 2020 because only subscriptions that were active in the beginning of January 2020 would be included in this metric.
Next, go to the expired_at column and remove all subscriptions with a date prior to the time interval you are analyzing. For example, if you are checking your churn rate for January 2020, you would remove all subscriptions that expired with dates prior to January 1st. This is your total active subscriptions in the beginning of the selected interval (in this example, Jan 2020).
Then, you would pull the Subscriptions - Churned export for the time interval you're analyzing, such as Jan 1 - 31, 2020. Sum the total of subscriptions listed in this export. This is your total of subscriptions churned over the selected interval.
This is all the data you need to calculate the % churn using the above formula.