Number of all employees on the plan

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Hello,

I need to calculate one average value for all employees on the plan, so I need to know how many of them are there on a plan.

Is there a possibility to calculate how many employees are on the plan or how many are direct+indirect employees of proxy manager?

I see this value in summary section - is it possible to retrieve it somehow in details column; or what logic is done behind this value (so I can try to use it in FF)?

Thank you in advance,

Edyta