I am quoting from Charles Cave's "How I use emacs and org to implement GTD"

 

He shows has two configuration lines:

 

#+PROPERTY: Effort_ALL    0:10 0:20 0:30 1:00 2:00 4:00 6:00 8:00
#+PROPERTY: Effort_ALL 0 0:10 0:20 0:30 1:00 2:00 3:00 4:00 8:00

with one #+COLUMNS: line in between

 

Can someone throw some light on this?