This is now the second key decision point as you are using the Media Creation Tool to upgrade to the Windows 10 Creators Update.
Most Windows 10 users will leave these as they are and retain their personal files and apps.
However, if you wanted to have a "clean install" you could select the "Change what to keep" link and choose to keep none of your personal data or apps.
This will deliver a version of the Windows 10 Creators Update just as if it had been clean installed on the device. You will see the entire Out of Box Experience and have to set the device up from scratch including your data, app installs, and customizations.
Once you have decided to move forward just select the "Install" button.