In Getting started with In-App Purchase using StoreKit views and the corresponding sample project, Store simultaneously enumerates Transaction.unfinished and Transaction.updates.
Since, "if your app has unfinished transactions, the updates listener receives them once, immediately after the app launches," it appears that Transaction.unfinished would also receive the same unfinished transactions causing handle(updatedTransaction:) to be called for twice for each transaction, causing consumables to be double-counted.
Is this a bug in the sample? Is there more information on concurrent execution of unfinished and updates?