To me that example does not remotely look like an overdate.
Just an extra piece in part of the 3 number.
A similar extra piece is on part of the 6 - yet that is not also considered
an 8/6 variety.
Also if it were a 2 underneath, then the lowest part of the 2 would
also be there as a horizontal line on left and right [see picture below].
Maybe just the wrong overdate picture chosen?
Hoping I am allowed to voice my opinion without getting shouted at.
Of course you're allowed to give your opinion, I even ask for it, so thanks.
Now to the non shouting, the varities have been established by the experts in the US, you find the mentioning in Red Book and the macro images on many sites, but as such I only use those from our allowed institutions, PCGS and USACoinBook, and they all seem to agree. I also look at the other sites featuring the year and variant to learn more or to be confirmed about the variety, I just can't use their images. Strange enough they all seem to agree.... about ALL the different overdates. Except for one, which I haven't put for revision in numista yet, but it'll come. It's the 25 cents (quarter) 1825, where the findings are contradictings, or I have misunderstood everything, which is quite possible!
I think it's very difficult for us to protest against the US definitions, although I also feel as frustrated as you from time to time, since I cannot see the all the "overdates" either.
The purpose of all these US documentations was to set all the year lines correct and back them up with the corresponding graphics and it's fun work, but sometimes frustrating as well, as this coin we're just discussing.
For me, this was one of those variants that I had to hold my nose and say OK. The fact that the Red Book says it's the "So-called 3 over 2" implies that it's not a true overdate but a variant that has become known as a "3 over 2".
P.S. Now that I've looked at it again for this reply, it does need to be changed. The top line in the box says Overdate 1862/1863 which is backwards. Maybe also add quotes around the word Overdate to show it's not a true overdate?