nabla: The quote says that you only get the seeds in your own pods if you cannot make a move that gives your opponent a move to make. For instance, all you have (as white) is 3 seeds in a1 and 2 seeds in b1. No possible move will give your opponent a seed.

Note that Oware is quite different from the Mancale game we play here. Oware doesn't have a collection pod, you can only score seeds with captures, which you do by ending your sow in an opponents pod that contains 2 or 3 stones (after seeding).

Another Oware link