This screen as shown in the image below indicates that a software update for the Android™ TV is available.
You can either skip the update and perform it at a later time by selecting LATER or update the software during the initial setup by selecting UPGRADE NOW. If you select UPGRADE NOW, the update will begin downloading.
Once the TV finishes downloading the update, it will then ask if you wish to install it. Select OK to accept and start the installation. Alternatively, you can select Cancel, and proceed later with the installation of the update.
IMPORTANT: Be advised that installing an update may take up to 30 minutes or longer depending on your network speed, during which you will not be able to use your TV and a screen with an update icon will be displayed.