Rule take a long time to complete

The Below rule takes 5 minutes.

STI Provision"->"OWP_Expense Amount"=(@XREF(EPBCSREPCube,"No Job","No Employee","No Component","No Cost Center","No Functional Area","No Future","No Gender",
"No Nationality","No Employee Group","STI Provision","Maintenance - BHRL","OEP_Plan"))/
("OWP_Basic Salary"->"No Functional Area"->"No Cost center"->"OWP_Existing Employees"->"OEP_Plan"->"Expense Amount"->"Total Jobs");

But if we edit the rule form ->"No Functional Area"->"No Cost center" to ->"Total Functional Area"->"Total Cost center"

ie.

STI Provision"->"OWP_Expense Amount"=(@XREF(EPBCSREPCube,"No Job","No Employee","No Component","No Cost Center","No Functional Area","No Future","No Gender",