The bucket size is the size in pixels of the rendering "swaths" as it were that will go across the render. 32 will stress the computer less than 124. I have 3 gigs of ram and I use 32. Opinions may differ ;o).

32 is a smaller swath, but it goes faster than 124 which is a larger swath, but takes longer. You have to find a happy medium.

Laurie