doc.FAQ.WhatDoesFieldSizeMaximumDo

This option is similar to the Expression Precision/Scale option. The Progress 4GL database engine allows the storage of character strings which are longer than the declared SQL width. For instance, creating a table with a char column will default to 8 but Progress will allow you to specify more than 8 characters. By specifying a Max value, with this option, the ODBC driver internally will override the value provided by the ODBC call SQLDescribecol and use the value provided.