This 18-piece set can hold, in total, 30 CUPS worth of whatever! Unless the whatever is Pyrex-devouring aliens.
There are many things you can do with nine containers and nine lids. Many, many, many things you can store and save in the BPA-free, non-porous glass. Things to put in the freezer, or the microwave, or the dishwasher if you just want to clean it off the sides before you nest and stack your containers.
But please. PLEASE. Do not under any circumstances stuff a Pyrex-eating alien into one of these containers.
Hopefully, though, that will never come up in your life. It really only applies in a few select government labs and most of those are under secret mountain military bases with very strict rules about people bringing their lunch.