Overall Budget Amount in WFC compensation

Summary

Budget

Content

Hi,

From where does current budget amount gets populated in workforce compensation.  If i navigate to 

Act as Proxy manager > Select a manager name > Viewing Plan (e.g. Merit with Lump Sum) > Tasks (Manage Budget icon) > Get Manage Budget Screen

The above screen displays Plan with total number of workers , Overall Budget ,Total Allocated and Available Budget amounts

I need to know from where does above highlighted values are populated ?

e.g. Overall budget shows an amount with a N% value assigned.  Which step governs this N value?