Dear Adarsh,
At Stage- 1: two share certificates will be issued for 10,000 shares each in the name of Mr. A and B respectively.
At Stage- 2: since all the shares are being transfered to Mr. C, on the back side of both Certificates name of Mr. C will be written only (also called Endoresement).
At Stage- 3 since the shares again are being transfered to Mr. D, on the back side name of Mr. D will be written.
At Stage- 4 Mr. D will submit the share certificates with the Company and request to split the existing share certificates into denomination of 15,000 and 5,000. This time both the Share Certificates will be issued in the name of Mr. D and by virtue of transfer endorsement will be made at the back side in the name of Mr. E and F.
Hence, in totallity 4 share Certificates will be printed.