How many circles are there on an original 1966 "Twister" mat?

The standard home version had 24.

However, the world's largest Twister mat is 20.5 metres x 8 metres with 1488 circles (24 circles wide and 62 circles long)
At the start you need 102 people to fill the Twister mat and play the game

Twister is a very simple game that can become very complicated as the players can easily get tied up in knots. The mat that forms the playing surface is decorated with six circles each of red, yellow, green and blue. The mat is durable, waterproof with a wipe-clean surface but it can also be a little slippery so care must be taken. The spinner arrow is easy to assemble and to use.

https://www.dbesttoys.com/store/family-and-fun-for-everyone/classic-twister-game/