When people click one of your short links and their regional information cannot be obtained, the clicks will be grouped together under the "No country data" or "No city data" group.
So, if you see 17 clicks with "No city data," this could indicate there were 17 clicks from 17 different cities, 17 clicks from the same city, or something in between -- there is no way to tell. Keep this in mind when analyzing your data.
A note about city data: City data is available for October 14, 2019 and after. Bitly started collecting city data on October 13, 2019, but that day's data is not for a full day. Clicks before that time will be grouped together under the "No city data" label.