Good idea to use that abacus to demonstrate the Lightning Network to the people. I think the hardest part of the LN model for most of the people is to understand that they don't need to open/close a channel each time they want to transact, if the channel is used in both directions. The concept of the Lightning network is ready for years now but people still don't have a clue about the whole thing, they are only waiting for it, because they think it will solve all problems of bitcoin. Education is really needed...