algorithms – Optimal TSP path with connection and link

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I just wanted a little clarification on the image above. I understand the general idea of ​​building a tree in DFS order and stopping once you run into a higher number than you had before. For example, when the path value becomes $ 14 or $ inf $ the algorithm stops because there was already a value path $ 11 $. But, I'm quite confused as to where these numbers came from (the lower cost limits). For example, the path from the top $ A $ at the top $ B $ has a length $ 1 $, but in the tree, the path of $ A $ at $ B $ has a lower limit of $ 10.

So, I would greatly appreciate if someone could let me know where the numbers come from in the branches and links search tree!