Hi,
i forgot to explain the riddle of the 50+ GB size.
2048 divided by 512 is 4. 59.64 divided by 4 is 14.91.
This is not completely plausible yet, because a USB stick of 14.9 GiB
would probably be sold as 15 GB stick.
There might also be a confusion of merchant's GB (1 billion) and
programmer's GiB (2 exp 30 = 1,073,741,824).
If your stick has 14 GiB (14 times 2 exp 30) then it has slighly more
then 15 GB (15 * 10 exp 9). 4 times 15 is 60.
So if we assume not only cluelessness with ISO 9660 but also with
GiB <-> GB, and given that gparted reports 59.63 "GiB" i'd say your
stick has actually 14,907,500,000 bytes = 13.88 GiB.
If this is true, then you should really try out other partition editors.
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And since the label of /dev/sdb1 says "Ubuntu 16.04" and "amd64" we have
an ISO with the layout invented by Matthew J. Garrett for Fedora:
Partition 1 reaches from block 0 to the end of the ISO.
Partition 2 is located inside partition 1 (which nearly all partition
editors do hate) and has the role of EFI System Partition.
(There is also an invalid GPT, which any partition editor should ignore.)
So /dev/sdb1 is misrepresented by gparted as much too short (this fault
is somewhat excusable) and most of the blocks outside /dev/sdb2 are
misrepresented as unallocated (this is boldly wrong).
Have a nice day
Thomas