I think this is correct.  I have seen it used more often in business or government situations but this seems to fit the definition.

Yeah, I subscribe to Dick's definition. When I wrote the constitution for our astronomy club, I described our decision-making process as follows:

Regardless of the number of members in attendance, those present shall constitute a quorum for voting on all matters of club business.

I wrote it that way because we're a small club and often need to make decisions quickly. During our "constitutional convention" everyone knew what I meant and passed that paragraph without discussion.

No, I think the term minimum number is a bit vague in that construction. To respond to your original question, I would prefer the term minimum enrollment or maybe the minimum class size.

In Glenn's defense, I think we can legitimately make a distinction between its careful and correct meaning and a deliberate misuse for humorous or metaphorical applications.  As we used to say in my family regarding some table manners (not all), "it's ok as long as you know better".  At the dinner table that meant "I won't complain about you doing that here at home, but if I see you doing it while we're eating out we're going to have to tighten up the rules here too until I know you can eat without doing it that way."  It seems to me something of that sort can be said about the misuse of certain words:  As long as you know it's technically not the correct one, I wouldn't complain about its use in this context just to make the point clear.  But if you end up confusing the point rather than clarifying it, or if you appear to think it's actually the right word, we may have to have a talk.

Of course, maybe we'll have a talk anyway, just for fun.  That is after all the whole point of this forum which Grant and Martha have so fun-lovingly provided for us.