How the NET_VALUE_MAN gets caculated in SAP CRM?

Hi Experts,

In an opportunity header there is a field NET_VALUE_MAN(Exp Total Value) which holds the sum of the target revenue of the all items of opp.

I would like to know, how the system calculates it? or which standard method or FM, is responsible for this.?

Field: NET_VALUE_MAN

Component: BT111H_OPPT

View: Details

Context node: BTCUMULATH

I tried to search , but till now not able to find it.

Could you please help on this.

Thanks

Sudhansu