According to Merriam-Webster, the idiomatic meaning of "a good number of" is similar to that of "a good many", both of which express the idea that there is a lot of something. For example:
An actress who has appear in a good number of [many] movies.
However, I would like to know if it's acceptable/natural to use it more literally to mean "a good/desired amount" of something. Since amount refers to quantities that are measured in bulk or mass, and shouldn't grammatically be used for things that can be counted (e.g. hours or children).
To give further clarification, below are two sentences that I wanted to use, but am not sure whether or not they adhere to rules of phrase usage.
A good number of community service hours to have would be around a hundred.
To mean I should aim for around 100 hours of community service.
A good number of students to have in a classroom would be under 40.
Since I can't say "a good amount of students...".
So what do you think about using those constructions? Is it acceptable to use them in such ways?