Data conversion failed from text to number

Hello, dear forum. I have this error:
data conversion failed from text to number.
how can I fix it? when I run my simulation it works properly but when I run optimizer this error happens. even I updated my Rhino in case the grasshopper has any problem. I will be thankful if anyone helps me.

You are reading out of a text box, so the List Item is actually selecting text, not number. Put a Num parameter (the one that says “.1”) between the text box and the List Item, to recast it into a number.

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Thank you @akilli. you helped me a lot.