Fewer or Less, Amount or Number?

Fewer and Number are used for quantities that can be counted.

Fewer people registered for the seminar than we anticipated.
You wouldn't believe the number of hours Deidre spent preparing for the presentation.


Less and Amount are used for quantities that cannot be counted.

My local grocery store is less crowded than the regional chains in the area.
Matt had a smaller amount of food on his plate than Shelly.