You, holding a large jar full of ants, grinning: tell me, how many ants do you reckon are in here?
Me, in a moment of contemplation: yes, a dozen. Yes.
You, now perplexed: there are obviously hundreds of ants in here- 693 exactly- how could you-
Me: ah, so there are a dozen.
You: What are on about? A dozen and six hundred eighty-
Me: right. So there were a dozen in the jar.
You: I see now.
Me: a dozen ants.
You: a dozen ants.