An expression used to indicate the awesome nature of a number of things, such as an event, physical object, or situation.
The delicious chocolate lava cake was quantity, as was the party on Saturday night.
To get a lot of something that is good. Used to express your feeling of joy because you just aquired more of something.
Guy 1: Dude, you are totaly taking advantage of their endless nachos promotion.
Guy 2: Quantity~~ (face beaming with joy)