Since this is not the first Nougat-based firmware for the Nexus 9 tablets on T-Mobile, the update is tiny, weighing only 52 MB. Even this way, the update comes with a few noticeable changes, such as support for sending GIFs from the keyboard.
http://www.notebookcheck.net/Google-Nexus-9-tablets-on-T-Mobile-get-Android-7-1-1.188301.0.html