In short, the JDBC connector fails to handle the extended range of UNSIGNED integers. Tested in LibreOffice, previously reported bug to them, they say it is NOTOURBUG. See report:
Short description: UNSIGNED Tinyint has value 0 to 255 but JDBC connector does not handle/report values 128 to 255 correctly. They are communicated erroneously or as negative numbers. Reporting here because LibreOffice says not their bug.
Same behavior identified in MySQL JDBC connector.
Windows 7 connecting to LibreOffice Base 4.3.5