Just like Cancelled Subscriptions, a canceled trial means the same: a user opt-out from prolonging subscription. That means you won't get a first payment (any other until a user restores a subscription).
Apple/Google will let you know about Refunds via server2server notifications. Handle, store and process them to build custom views with Cancelled Trials analytics.
Adapty does everything for you automatically. Simple install SDK for your platform, open Advanced Dashboard and you're ready to go!