Should the weight on the blue community's relationship to itself be 12, not 14? I can understand all the other weights, but this one looks wrong (or I've misunderstood the process).

Definitely a typo in the course materials. The top-right weight for the blue nodes should be 12, not 14 and the the bottom-right weight for the blue node should be 24 instead of 26.

Thank you for pointing this out. We will correct the content.