Although it is not a major update it has a pretty big importance because it brings full access to Verizon Wireless 4G LTE for all Motorola XOOM tablets connected to Big Red network.
The new upgrade build number HLK75F is quite a small only 8.9 MB in size but it brings what everyone wanted access to 4G LTE speeds on their XOOM Android Honeycomb devices. Its an over the air (FOTA/OTA) update so you should be able to manually pull it any time by going to Settings > About tablet > System updates. Select”Install Now”. Your device will Power-off and back ON and the installation process will begin.
source Verizon Support