Although this video was tricky to figure out, I finally got it. What happened was that they did not “carry over”. The easiest way for me to explain this is by addition. If you have a lot of numbers like they did you have to do something special when you add. First you add the ones column. If the sum is more than ten you carry the tens value over to the tens column. What they did wrong is that they counted what should’ve been tens as ones. Another set of numbers that could work is 4x16=28; this is not true because 16x4 really equals 64.