By default, JetPack-L4T flashes Jetson TX2 with a 16GB root filesystem. Even though TX2 has 32GB eMMC storage capacity, not all the tools may support the full 32GB filesystem partition size, or when you go to clone & restore a file of that size may be problematic. However, during flashing you can opt to increase the RootFS size from 16GB to the maximum.
Setting APP Partition Size
When flashing with L4T, use the -S parameter to flash.sh to manually specify the size of the root filesystem.
Note that the maximum acceptable size for Jetson TX2 is 29318MiB.
$ sudo ./flash -S 29318MiB jetson-tx2 mmcblk0p1
Creating Another Partition
Rather than increase the size of the Linux root filesystem, it's also possible to format the remaining eMMC space as a secondary partition. This may be useful for storing data files that can be separate from installed program files. Keeping two separate, smaller partitions can be useful when you need to backup and clone the device.
Resizing Existing Partition
By backing up the main APP partition and resizing it on the host, it's also possible to resize the partition without re-creating it's contents from scratch. See this forum thread for the procedure: