It would also be a fair call to ask what is the part they don't understand, in order to clarify. Without that is difficult to help.
You agree that Nokia may increase the percentage of Net Revenue payable to You for either operator or credit card billing without having to amend this Agreement. For purchases made via operator billing, You acknowledge and agree, that payment and bad debt information received from operator billing arrangements may be based on aggregate amounts and not itemized, and that if Nokia is unable to determine the exact amount directly attributable to all Content, then Nokia may allocate and apportion such revenues or bad debt according to an equitable prorated method across Content sold through a particular operator. I'd love to sign up for equitable prorated bad debt to distribute a free $0 app.