amend proper english and capitalisation

docs/UserGuide.md

@@ -461,7 +461,7 @@ StaffConnect data are saved automatically as a JSON file `[JAR file location]/da
 <div markdown="span" class="alert alert-warning">:exclamation: **Caution:**
 If your changes to the data file makes its format invalid, StaffConnect will discard all data and start with an empty data file at the next run. Hence, it is recommended to take a backup of the file before editing it.<br>
 Furthermore, certain edits can cause the StaffConnect to behave in unexpected ways (e.g., if a value entered is outside of the acceptable range). 
-The Application will not prompt the user if the format of the data file is incorrect, but instead provide the user with a empty StaffBook.
+The application will not prompt the user if the format of the data file is incorrect, but instead provide the user with an empty staff book.
 Therefore, edit the data file only if you are confident that you can update it correctly.
 
 </div>