Employee Hierarchy - Fixed Hierarchy Level is always zero

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We have loaded employees' and managers' data populated in the resource object and running the ESS job to populate the employee hierarchy. I see manager hierarchy populated but column "Service Resource Hierarchy"."Fixed Hierarchy Level" is always zero. For a manager, I am expecting a none zero value but for all the records it is showing zero. What could be the reason?

jtf_rs_rep_managers_cf.FIXED_HIERARCHY_LEVEL

Take a look at the attached image, ideally, Evan's Fixed Hierarchy Level should be greater than zero as he is managing few employees.

Do we have to do anything special to populate this attribute?