Question

what information does the subscript tell us in a chemical formula?
unt of compounds
amount of molecules
amount of elements

Explanation:

Subscripts in a chemical formula are small numbers written below and to the right of an element's symbol. They specify the number of atoms of that particular element present in one molecule or formula unit of the compound. For example, in $\text{H}_2\text{O}$, the subscript 2 indicates 2 hydrogen atoms per water molecule. This matches the description of indicating the amount (number) of the element within the compound.

Answer:

Amount of elements