The PN32 gloves do not need to use all of the sensor slots to work. The image below is a reference of which sensors are required for the gloves to work and which ones are optional.
The fingers have a total of 7 slots. 3 of the slots are required, and the rest are optional.
There are a few advantages of using less finger sensors on the hands:
1. It gives you more spare sensors to use elsewhere on the body.
2. It provides a cleaner capture