Why is only this one item missing after merging?
It’s not. You’re also missing one of the values from the first sublist. List.SetUnion returns each unique item that appears in the two input lists. You just happen to have some rounding issues that are causing your second sublist to return all values.
What are you wanting from SetUnion? It sounds like you’re expecting something else.
List.Join perhaps?
That would be my guess, but for the sublists, which is a little more involved.
Ah. List.Create > Liat.Transpose then. 
I did say “a little”. 
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I am still solving the problem of extracting the window area in the room. The normal window area is length times height, but when the windows are arranged vertically, the area becomes thickness times height, so I set up filters for length and thickness separately to obtain each length of the window, and finally combine the two sets of values.
Your images aren’t processing all the way. Confirm the preview before you hit post. 
I don’t know why, it doesn’t show up after sending it twice. It’s maybe a problem with the VPN. It’s not important anymore. I replaced it with a simple python node; but I still want to continue to learn how to get the detailed information of windows on a room basis, including Window opening area, etc., can Dynamo directly extract the information in these families? Are there any articles that introduce the method of shutting down first? Thanks！
I’m assuming you press send too fast, not allowing the upload to complete first, like Jacob said
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