To give depth here: limiting people isn't the only relevant dimension. You could argue cities are a gather of more than 1000 people. More important is density,

To give depth here: limiting people isn't the only relevant dimension. You could argue cities are a gather of more than 1000 people. More important is density, how many people each person is expected to interact with, is there a buffet, etc. If you're running an event with 999 people, hopefully you're organizing to be less bulging at the seams with these other dimensions