Helper usage for a shutter position

[klaus1956]

Hello

I am quite new in HA and currently work on a shutter automation based on sun intensity.
We have a Shelly-operated shutter on an east window and an Senec PV-system with east & west pannels.

Idea is to close the shutter partly in a time periode in the morning (e.g. 9:00-11:00 - determined by Helpers) based on the Electricity production (by Helper e.g. > 2500W) to prevent dazzle. Setup with these helpers works fine but I would like to pot in a Helper for the shutter position too.

Action section of the Automation is following:

action:

• device_id: 2215a3658ba78044d8e3dea40b4d3daf
  domain: cover
  entity_id: cover.shellyswitch25_483fda821569
  type: set_position
  position: 65
• condition: state
  entity_id: input_boolean.rk_flag
  state: 'true'

Based on some copy from a Youtube tutorial I replace the position section by:
position: |
{{ states('input_number.rk_teiloeffnung') }}

But I get following Error (cannot be saved):

Is anyone able to help?

Thank you
Klaus