Hi @Jaspreet Kaur B ,

 u_summary_notes, u_impact_extent, u_impact_type fields are custom tables. Custom fields won't refer in ServiceNow product documentation.

Note: Tables (or) Fields started with "u_" are custom tables in ServiceNow.

Please appreciate the efforts of community contributors by marking appropriate response as correct answer and helpful, this may help other community users to follow correct solution in future.

Thanks & Regards,
Sumanth Meda