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value error
Hello,
I am very new to expressions so excuse me if this question is stupid.
Recently, I was watching a tutorial and tried to go along but although I copied the code line by line there was an error message every time I tried. (see below for expression)

Luckily there was also a prepared project file that contained the expression which is 100% identical with the one I wrote myself.

The only difference is that it works, even when I copy it to other projects.
Since I really want to learn more about expressions my question is: Why doesn’t the expression I wrote work even though it is completely identical to the one I got from the project file and what does the error message mean.Thank you for your help.