Forfeiture amount per share is the amount to be received by the company on forfeiture of each share.
$$Forfeiture\quad Amount=Application\quad Amount$$
Substitute the values in above equation
$$Forfeiture\quad Amount=Rs30$$
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
$$Forfeiture\quad Amount=50shares \times Rs30= Rs1,500$$
$$Forfeiture\quad Amount\quad for\quad 20share= 20shares \times Rs30= Rs600$$
$$Forfeiture\quad amount\quad on\quad reissue=20shares \times Rs10=200$$
Profit on the reissue is the profit earned by the company when the forfeited shares are reissued
$$Profit\quad on\quad reissue=Forfeited\quad Amount\quad on\quad forfeiture-Forfeited\quad amount\quad on\quad reissue $$
Substitute the values in the above equation
$$Profit\quad on\quad reissue= Rs600-Rs200= Rs400$$
Hence, the profit earned on the reissue of shares is Rs $$400$$.
Share Forfeiture a/c Dr. Rs400
To capital reserve a/c Rs400.