270 is 3/4th of a circle, in the middle its like this --- to the left its like this / and to the right its like this \ (center line)
The ones where degrees arent mentioned spin endlessly but are aka 360 degree wheels.
Games that used a 360 wheel, like pole position, cant use a 270 wheel. games that use a 270 wheel go apeshit when you spin too far or have other issues.