This "quick tutorial" introduces the general idea of a call and explains the most common cases. It does not explain or illustrate all cases. For additional details and/or examples, refer to the links in the "MORE INFO" box.
The difference is simply in how far they go after that. For a 1/4 Top, they stop when they meet the first person. This is very quick.
For a 1/2 Top, they stop when they meet the second person.
For a 3/4 Top, they stop when they meet the third person.
For a full All 8 Spin the Top they stop when they meet the fourth person -- who will be the person with whom they started originally.
Note that the fraction refers only to the final turning action. The initial turn, done by the end and center, is always 1/2 (180 degress).