When you receive a new version of your Kindle ebook, you need to replace the old version with the new version. If you do not, you will erroneously read the older version.
Here is what you do:
1. From within your Kindle reader or Kindle software on your PC, delete the old version from the Kindle library by right clicking and choosing "delete".
2. Double-click the new version to import this into the Kindle viewer.
Now you will be reading the new version, not the old version.