Both statements are true because they are referencing different transactions.

• the transaction saw a control record updated to show that a batch has been completed. This transaction is running an analysis on the completed batch.

• the transaction read an earlier revision of the control record. This slow running transaction is still adding data to the completed batch.

There is a really good step by step explanation of this example on the Postgres wiki https://wiki.postgresql.org/wiki/SSI#Deposit_Report.