How does medium tracks that I have read 5 blogs this month?

There are two ways in which medium can track a user

• Userid
• IP address

Lets concentrate mainly on IP address based tracking. What I found was even if I read 5 articles this month. If I open medium in an incognito window I am able to view the blog contents.

Also we know that incognito browsing does not hides our IP address, its "no VPN". so my question is how is medium unable to track me, when I use incognito and let me view the blog?