Forfeiture amount per share is the amount to be received by the company on forfeiture of each share.
$$Forfeiture\quad Amount=Application\quad Amount\quad +\quad Allotment\quad Amount$$
Substitute the values in above equation
$$Forfeiture\quad Amount=Rs10$$
Forfeiture amount is the money received by company on forfeiture (cancellation of share) or on the reissue of share.
$$Forfeiture\quad Amount= No.\quad of\quad shares \times Forfeiture\quad Amount$$
Substitute the values in the above equation
$$Forfeiture\quad Amount=200shares \times Rs10= Rs2,000$$
$$Forfeiture\quad Amount\quad for\quad 80shares=80shares \times Rs10=Rs800$$
$$Forfeiture\quad Amount\quad on\quad reissue=\quad 80shares\times Rs5\quad = Rs400\\ $$
Profit on the reissue is the profit earned by the company when the forfeited shares are reissued
$$Profit\quad on\quad reissue=Forfeited\quad Amount\quad on\quad forfeiture\quad -\quad Forfeited\quad Amount\quad on\quad Reissue$$
Substitute the values in the above equation
$$Profit\quad on\quad reissue=Rs800-Rs400 = Rs400$$
Hence, the profit earned on the reissue of shares is Rs $$400$$.
Share forfeiture a/c Dr. Rs400
To share capital a/c Rs400.