Linux Mint 18.3 x64 (base on Ubuntu 16.04 package base)
Postgresql v 9.5.14
unixODBC v2.3.1-4.1
psqlODBC v1:09.03.0300-1
I created a simple table containing one column of type character (n). When I ask for the width of the column via (ODBC)SQLColAttribute function, it answers (n*6) , so if defined as character(1) the call reports length 6, character(2) reports 12, character(4) reports 24, etc.
I see the same kind of results when using a varchar(n) field (character varying (2), etc ) as well .