The option to display topics in multiple columns uses the old Bootstrap 2 column classes (i.e. "row-fluid", "span3", "span4" and "span6". This doesn't work in newer versions of Boostrap (used by the Boost theme).
These should be replaced with the newer Boostrap "col-[xs|sm|md|lg|xl]-*" class names.
The option to display topics in multiple columns uses the old Bootstrap 2 column classes (i.e. "row-fluid", "span3", "span4" and "span6". This doesn't work in newer versions of Boostrap (used by the Boost theme).
These should be replaced with the newer Boostrap "col-[xs|sm|md|lg|xl]-*" class names.