But for developer, this information (16G) is not enough.
Just like we right-click the removable disk and then select "Properties". We can also check the total byte information of android phone storage.
First, enable USB debugging and use adb tool to check emmc size.
$ cd sys/block/mmcblk0
$ cat size
cat size
30785536
The number 30785536 is block number.
Total size is 30785536*512 = 15762194432 bytes