The boardstyle setting controls the format of game board information sent by FIBS. For people playing on "dumb terminal" software, boardstyle 1 or 2 display the board as a series of X's and O's that are human readable.

MacFIBS only understands boardstyle 3, which is a compact machine readable form. MacFIBS should automatically detect and set the boardstyle, so you should never need to alter it manually.