config: fix config example (#31545)

close #31546

config/config.toml.example

@@ -292,7 +292,7 @@ distinct-agg-push-down = false
 # If using TiKV as the storage, the entry represents a key/value pair.
 # NOTE: If binlog is enabled with Kafka (e.g. arbiter cluster),
 # this value should be less than 1073741824(1G) because this is the maximum size that can be handled by Kafka.
-# If binlog is disabled or binlog is enabled without Kafka, this value should be less than 10737418240(10G).
+# If binlog is disabled or binlog is enabled without Kafka, this value should be less than 1099511627776(1T).
 txn-total-size-limit = 104857600
 
 # The limitation of the size in byte for each entry in one transaction.