The first one is a 1 minute load average, second is 5 minutes, third is 15 minutes, just like the uptime command. They do not have any special correlation in htop other than to stand out from each other.
This is a good read on understanding what load is:http://blog.scoutapp.com/articles/2009/07/31/understanding-load-averages
Original source: http://serverfault.com/questions/204753/why-does-htop-have-three-load-averages
