You have the right idea. Most members are in only one (pool 1 or 2); I think you were moved back and forth a couple of times while we were working to stabilize pool 1, and that's why you thought you were in both. Shares are capped at 100 per member in all but the bottom pool. (So @sneakyninja has 100 shares in pool 1, and more than 100 in pool 2, but when pool 3 all but 100 of their pool 2 shares will spill into pool 3).
The only way to be in more than one pool (besides being moved between them sometimes) is to exceed that 100 share limit and spill over into the next pool.