Administration > Environment Variables > APTTBLWIDTH — Specifying the Default Width for New Tables
  
APTTBLWIDTH — Specifying the Default Width for New Tables
Specifies the default value for the set tablewidth option. The default is 100% of the view width for all table models. If you specify a width for APTBLWIDTH, new tables will have the width specified (for example, 80%, 5in, 350pt, 6cm).