Final answer:
The third set of NDC numbers in chemistry indicates the presence of a methyl (CH3) group on the third carbon atom and an OH group on the second carbon atom.
Step-by-step explanation:
The third set of NDC numbers in chemistry indicates the presence of a methyl (CH3) group on the third carbon atom and an OH group on the second carbon atom. These numbers are part of the National Drug Code (NDC) system, which is used to identify drugs and medications. The third set of numbers provides important information about the chemical structure of the compound.