In that particular instance you are looking at a device file, not a normal file. Device files are identified by a Major and Minor device number. The first number 250 is the major number, the second number 0 is the minor number.
One example of this is your SD card, where on a standard (non-NOOBS) Raspbian install you will see something like the following
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pi@raspi9:~ $ ls -l /dev/mmcblk*
brw-rw---- 1 root disk 179, 0 Mar 29 2017 /dev/mmcblk0
brw-rw---- 1 root disk 179, 1 Mar 29 2017 /dev/mmcblk0p1
brw-rw---- 1 root disk 179, 2 Mar 29 2017 /dev/mmcblk0p2
In this case, the Major number that identifies the card device is 179. Minor number 0 is the whole raw card. Minor number 1 is the first partition, Minor number 2 is the second partition.