They're the peak value in dB attained by the associated track. If it reads -6.2, that means the highest level attained by the track, taking the fader setting and any effects into account, was -6.2dB.
 
You might want to check out my first post in the 31 Days of Tips thread about the meters. There was another post about peak hold, which is what you're seeing.
 
A reasonable peak value is less than 0 but more than -18. Those are arbitrary numbers, there's no "headroom police."

Craig ...   You are probably the most responsive person with whom I have ever had the pleasure of dealing.  Thanks for both your wisdom and your promptness. 
 
 

You just happen to post your questions when I'm online, so I think luck enters into it :) Or maybe we just keep the same hours.

BTW  is there a link to your set of tips?  I've tried the forum's search feature and am having trouble finding the Tip for Day 1

It's a sticky at the top of this here very forum. We're on day 21 of the 31 days of tips, so you better hurry up and join the party...the open bar closes on Day 29, and the DJs pack up on Day 30. Well, unless Cakewalk is willing to pay for overtime for the security.
 
Don't forget to get your parking validated, otherwise it'll cost you $20.

Jlien asked about this a while ago on an empty track, as is shows a "dent"... It was not till I actually looked it up that I realized you can click on it to zoom to the peak in the track (nice feature if you ever find yourself clipping on a transient).