In the manual of ROOT 5.14.00 one can read that
"TH1S : histograms with one short per channel. Maximum bin content = 65535"
The next 3 lines demonstrate the opposite result
The result is 32767. I saw the source and found there the usual limitation of short int values that conflicts with manual and conflicts with the comment of the source. Fortunately it was checked before a list of TH1I matrices having the maximum around 50000 were converted into TH1S.
In principal, the TH1(2) objects of unsigned short would be very helpful.