Hello Lezoch
"0Amount" is the Unit Price ( sales price) of material.. this price keep changes provided if any promotion or offers granted to the customers.. so accordingly there is validity period fixed for every price against the material.
the concern is.. when we have a particular Material price valid from (i.e 01.09.2015 till 30.09.2015 at Unit Price is 5.00 USD) and if the user execute the report giving date 15.09.2015 in selection parameters.. the output should show USD 5.00 is active on date 15.09.2015.
Regards
Sachin