The file size is 14,167,736. The "size on disk" reported by Windows depends on properties of your hard disk such as the cluster size. The 1Tbyte drive in my Windows 10 PC says 14,168,064.
The incorrect 10.7 Mbyte figure in the post by Obihai is probably the result of a careless and incomplete edit by whoever updated that post.
No, there is no way to force the update past a checksum error.
It should not be necessary to update to an intermediate firmware version.
HOWEVERYou should not need to manually update the firmware as even for OBi20x devices out of warranty, Obihai has arranged a semi-automatic update to address the recent GV change. Go to your Dashboard at
obitalk.com and you should find a yellow triangle containing an exclamation mark. Clicking on that should initiate the firmware update.