Polish doc

Closes gh-5375

spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -1073,7 +1073,7 @@ NOTE: you can also specify `debug=true` in your `application.properties`.
 
 When the debug mode is enabled, a selection of core loggers (embedded container, Hibernate
 and Spring) are configured to output more information. Enabling the debug mode does _not_
-configure your application log all messages with `DEBUG` level.
+configure your application to log all messages with `DEBUG` level.
 
 [[boot-features-logging-color-coded-output]]
 ==== Color-coded output

spring-boot-docs/src/main/asciidoc/using-spring-boot.adoc

@@ -667,8 +667,8 @@ configuration to replace specific parts of the auto-configuration. For example,
 you add your own `DataSource` bean, the default embedded database support will back away.
 
 If you need to find out what auto-configuration is currently being applied, and why,
-start your application with the `--debug` switch. This will log an auto-configuration
+start your application with the `--debug` switch. This will enables debug logs for a
-report to the console.
+selection of core loggers and log an auto-configuration report to the console.
 
 
 

spring-boot/src/main/java/org/springframework/boot/logging/LoggingApplicationListener.java

@@ -47,8 +47,10 @@ import org.springframework.util.StringUtils;
 
 /**
  * An {@link ApplicationListener} that configures the {@link LoggingSystem}. If the
- * environment contains a {@code logging.config} property a then that will be used to
+ * environment contains a {@code logging.config} property it will be used to
- * initialize the logging system, otherwise a default configuration is used.
+ * bootstrap the logging system, otherwise a default configuration is used. Regardless,
+ * logging levels will be customized if the environment contains {@code logging.level.*}
+ * entries.
  * <p>
  * By default, log output is only written to the console. If a log file is required the
  * {@code logging.path} and {@code logging.file} properties can be used.