If a portion of an entire fund or stock is specifically bequeathed, the receipt by the testator of a portion of the fund or stock shall operate as an ademption only to the extent of the amount so received; and the residue of the fund or stock shall be applicable to the discharge of the specific legacy.
     Illustration
     A bequeaths to B one-half of the sum of 10,000 rupees due to him from W. A in his lifetime receives 6,000 rupees, part of the 10,000 rupees. The 4,000 rupees which are due from W to A at the time of his death belong to B under the specific bequest.