Hi,
I had given some example.
HRA exemption is computed by function INHRA based on infotype 581 - Housing in India Payroll.
Indirect valuation is a method to valuate a wage type from other wage type using %.
As per your question (given in the top) -
Number/RTE & Unit is additional fields available in any payroll wage types which are used for storing additional data and/or used for further valuations.
regards,
Bala.