Updated README.md

Author: mickaelandrieu

README.md

@@ -14,11 +14,18 @@ This is the CLI tool to train on certifications.
 ## Using Composer
 ```
 $ composer create-project certificationy/certificationy-cli
-$ php certificationy.php [--number=20]
+$ php certificationy.php
 ```
 
 ## More run options
 
+### Select the number of questions
+```
+$ php certificationy.php start --number=10
+```
+
+The default value is 20.
+
 ### List categories
 ```
 $ php certificationy.php start --list [-l]