Claim of foreign retention tax by Indian Company

We have entered into a contract for rendering  consultancy services to  a Kenyan Company. Billing is made by us in USD. TDS is deducted and paid by the Kenyan company in their local currency to their government while paying our bills. This TDS is claimable by Indian company as per DTA with Kenyan Govt. The question is what is the basis for conversion. What rate and which currency has to be adopted. Can any one clarify.

M.A.Padmanabha Rao

Chartered Accountant