Auto Update Deal Name on Create/Edit

Auto Update Deal Name on Create/Edit

Hi there,

I know this question has been posted multiple times and I've been trying many of the proposed similar scripts for a while now but nothing seems to work... what might I do wrong?

The error I receive is this:
"Unable to cast the 'TEXT' value into a 'Long' value because the input is in an invalid formatat lineNumber 3"

thanks a lot for your help!