As far as the total achievements go, I think it is a true sum of all the instances of each achievement. However, next to each achievement, it only shows the most significant power of two in the binary representation. So, if you have 70 +5 posts, it will only show 2^6 next to that achievement, but will contribute the full 70 points to the total.
It's the number of nodes that can be connected into a single machine multiplied by the theoretical peak performance of each node (implying zero actual communication). The limit on the number of nodes can be limited by a range of things, from how many nodes are addressable by the networking hardware to an #IFDEF on the maximum number of nodes the software is willing to support.
The statement is that the xc30 can _make it_ to 100 PF. Nobody will build a 100 PF machine (i.e., 1600 cabinets, 8x more than Jaguar) with this product line, there will be upgrades before then. 32k sq ft of machine room space and cooling is too expensive.
So submit a better one... I'm sure that these are driven by user submissions just like always.