Quantity was the amount of something.
In 2269, James T. Kirk noted in his captain's log that "The USS Enterprise is in the grip of a raging epidemic. Three crewmen have died and 23 others have been struck down by Rigelian fever. In order to combat the illness, Dr. Leonard McCoy needs large quantities of ryetalyn, which is the only known antidote for the fever. Our sensors have picked up sufficient quantities of pure ryetalyn on a small planet in the Omega system." (TOS: "Requiem for Methuselah")