Fortune teller's surname _ Fortune teller's surname

What's the matter with measuring your hand with a ruler to calculate your surname?

The premise is this:

1. Give him a card with his surname from more than a dozen cards in his hand. Each card has about 30 surnames.

He handed you a so-called eight diagrams, and asked to put it horizontally in the surname list on the ground. This surname table consists of 5×6 surnames grids, each grid has 4×5 surnames, and there are 20 surnames in total.

Then take a soft clay ruler and measure the total length of the five fingers of your left hand in centimeters, and then you can measure your last name according to the gossip.

Answer:

For example, in the first box of the gossip list, your surname is "Qiansun Zhao, Li, Zhou, Wu and Zheng Wang", and one of the cards you choose is "Zhao, Liu, Wang, Mao,". Zhao is repetitive, so you must be surnamed Zhao.