No it was right to left, on the second page w/super pi.
Like I said, the wording on the graph is very confusing, but it shows the DDR2-667 CL5 being the 2nd *worst*, better only than DDR2-400 CL5. The DDR2-800 CL4 is the *best* of all of them. Shorter times (faster completion of benchmark) are better; shorter times are to the left of the graph, longer times are to the right.
You think the memory will overheat if I overclock it?
It shouldn't. Most of the heat is carried away through the metal traces to the MB, anyway (the spreader doesn't do much if the chips are in [non-heat-conductive] plastic packaging, which almost all are).