16 GB USB flash drive capacity down to 938 MB
I managed to do it with diskpart. What I was missing is the command to create a new partition. So here is a run-down of all the commands I used, step by step.
Beware that when typing
select disk 1 (step 4), your disk number may be different. Selecting the incorrect disk might erase your whole computer's main disk drive, losing all your data on it.
I assume you know how to get to the Run prompt since you have arrived at SU. But if not, just press and hold down the Windows key on your keyboard. While still holding the Windows key, press the R key. Voilà! La Run prompt! L'invite de commande!
select disk 1(Careful! Choose the correct number here. See note above.)
list partition(Inspect the results to double-check this is the right disk)
list partition(There should be none)
create partition primary
list partition(There should be one)
format fs=fat32 quick
list partition(There should still be one)
In case you haven't realised it yet, you have to press the Enter key on your keyboard after each command line above.
Here it is now:
Shows up as a 14.6 GB drive.
And it looks good in diskmgmt.msc too. So it's all good now.
When you write an image to a flashdrive, it will create the partition based on the specifications on the image. In your case it creates a partition of 938 MB.
Because flashdrives will only show the first partition, you cannot access the rest. However, using computer management->Disk management, you normally can increase the partition and include the unallocated space. Seeing your image, it may not be possible with this particular image unless you somehow made an error when trying to flash the image.
Try to remove all but the F: Partition, then right click it, and use enlarge.
It is possible the image won't work anymore, but you can always delete all partitions and flash the image again.