CL- and VL- in kmeans clusterdump output

Hello,

I am using kmeans to cluster twitter data (usernames/tweets).

Some of my clusters are labelled VL-xxxxxx and some of them are
labelled CL-xxxxxx. I understand clusters that are labelled VL-xxxxxx
are 'converged', but I'm not really sure what that means. Any advice?
Also, what does CL- servce to indicate?

Many thanks.