What does uptime command results mean
They are the load averages over the last 1, 5, and 15 minutes, they are not related to your cores.
From the man page:
uptime gives a one line display of the following information. Thecurrent time, how long the system has been running, how many usersare currently logged on, and the system load averages for the past1, 5, and 15 minutes.For more information see man uptime.