Problem with my Tableau

Hi, I encountered a few problems.

First, my Tableau program (Public Edition, 2025.1.2 (20251.25.0520.1026)) reads the FTSE100 and Gspc500 columns as string values. I have to manually set these columns to Number (decimal).

Then, when I drag the Gspc500 from the left panel into Rows (as you do), a new dialog appears: "The field being add contains as many as 2758 members and the recommended maximum for this shelf is 1000. What do you want to do" with 4 options: Add all members, Filter and then add, Disable automatic updates and then add, Do not add

I choose the first one: All all members. THen I have the first line of Gspc500 as you have. But when I drag and hover the Ftse100 on top of the y axis as you do, I can see the 2 green bars sitting next to each other. It is fine, but when I release the mouse click, nothing changes. THe second line does not appear.