It's not the number of people on the IRC network... it's the number of people from your IP. This happens on a home network and also on work/school networks where everyone has the same outside IP address.
Not sure if this will help, I have seen three people on the same channel
living in different homes all with the same IP. I thought the first two
were the same person, a ghost and a recoonect.
They were kind enough to explain it was the way their dial up service worked.
They were all from Australia.
If you do not have a static IP meaning it changes each time you connect you could try closing your internet service and reconnect
or try connect to the internet on a different server in your providers group. If your IP is static you could try changing it,
this should be possible but I'm not sure how. Maybe check your ISP's help page or contact your provider for information.