Same, I am getting 23 too. I think the problem is due to the UI is lagging and thus the second addition click event is not registered. e.g: 4+5+6 will return y

Same, I am getting 23 too. I think the problem is due to the UI is lagging and thus the second addition click event is not registered. e.g: 4+5+6 will return you 56. Edit: Did it without using the "=" as other has pointed out.