Subsites Google Analytics Settings?

In the setting it says: Network setting "This is the code you’ll use to see the entirety of your network (as opposed to the main site only).

If you are using a subdomain install and want to also track their activity you’ll want to also check the radio button next to ‘Subdomain tracking‘"

My question: On subsites like site.com/username

Do you need to do anything special or is that above only for sub domains.

Thanks