When the board finds that any claim presented is not payable by the county, or is not a proper county charge, it must be rejected. If they find it to be a proper county charge, but greater in amount than is justly due, the board may allow the claim in part and draw a warrant for the portion allowed, on the claimant filing a receipt in full for his account. If the claimant is unwilling to receive such amount in full payment, the claim may be again considered at the next regular succeeding session of the board, but not afterward.