@Sandra here are Tape cheat sheet for calculation and also here.
I assume you have date field in your app, so I would use date field and add calculation for trigger date:
It is hard without seeing your workflow but in that case if you want to trigger other flows based on date I would use When a date field arrives trigger and than call other flows
You can just take the collected_touch_template_field_days_decimal_value and add it to your sequence_field_focus_date_start_date within the create record you can call the collected value with the β@β no need for the script.
however, as regards your script it does look to me like there is a small mistake anyway: