Subject to paragraph (2), the certificate of claim issued by the Secretary to any mortgagee shall be for an amount which the Secretary determines to be sufficient, when added to the face value of the debentures issued and the cash adjustment paid to the mortgagee, to equal the amount which the mortgagee would have received if, at the time of the conveyance to the Secretary of the property covered by the mortgage, the mortgagor had redeemed the property and paid in full all obligations under the mortgage and a reasonable amount for necessary expenses incurred by the mortgagee in connection with the foreclosure proceedings, or the acquisition of the mortgaged property otherwise, and the conveyance thereof to the Secretary. Each such certificate of claim shall provide that there shall accrue to the holder of such certificate with respect to the face amount of such certificate, an increment at the rate of 3 per centum per annum which shall not be compounded. The amount to which the holder of any such certificate shall be entitled shall be determined as provided in subsection (f).