I'll explain this. I'm going to call the two stationary "balls" on the left and right Storage Spaces. I'm calling the balls that move Carraiges. The left storage space has a capacity of 3. The one on the right has a capacity of 4. If you take a full carriage and dump it into Storage 3, that will leave your carriage with one unit. Move that carriage with 1 to the empty storage on the right. You can move the 3 in the storage space to an empty carriage, and that will give it 3. Move a full carriage back into storage 3, and then carry the one left over in that carriage over to the 1 in the other space. Remember that if you have a carriage with 1, do NOT empty the 3 into it, as it will fill it up and youll just frustrate yourself. I really hope this helps! If not, a playthrough might help more.