The word simple is incorrectly substituted for single in the following instances:

In Ch 9.4. Filtering Debezium change event records: To enable you to process only the records that are relevant to you, Debezium provides the filter simple message transform (SMT). (filtering.adoc L18)

Ch 2.1.2. How Debezium MySQL connectors handle database schema changes: If consumers do not need the records generated for helper tables then a simple message transform can be applied to filter them out. (mysql.adoc L111)