How big are shenzhou spaceship stamps?

The size of shenzhou spaceship stamps is19.5mm. The two stamps commemorating the first flight of shenzhou spaceship, China have an area of 877.5mm, and the bottom length is 45mm. The area of a triangle is the base times the height and then divided by 2. The area of these two triangular tickets is 877.5 square millimeters. Let the height of the triangle be x, and the formula is 45X=877.5, X= 19.5, one stamp.

Stamp source:

In order to commemorate the first anniversary of the successful first flight of Shenzhou, the first experimental spacecraft of China's manned spaceflight project, a stamp commemorating the successful first flight of Shenzhou was issued on October 20th, 2000/KLOC-0.

A set of 2 rockets respectively depicts the Long March launch vehicle used for shenzhou spaceship's first flight, the moment when it broke away from the launcher and soared into the sky, and the scene of shenzhou spaceship roaming in the vast space.