"Critical Path Number" - P6 EPPM 23.12 (Client)

Using P6 client (for EPPM) 23.12.1.48893

How are the "Critical Path Number" column/values calculated and populated? I am trying the new 'Activity Critical Path' toolbar and cannot seem to get the "Critical Path Number" column to populate.

I cant find any reference in the Oracle docs except here which doesn't go into detail for this column:

Schedule settings are:

- Ignore relationships…unchecked

- Open-ended…unchecked

- Retained logic

- Define critical as… 0h

- Calculate float based on…. Each Project

The schedule I am testing with has a clear critical path, and additional activities with float. Everything is linked.