upgrade 2011 with 2010

I had 2010 and a popup came up to upgrade to 2011 which I did. 

 

Recently as I noticed my version of 2010 was getting within a couple of months of expiring I purchased another 3-user license pack (2010).  If I install it to renew will it update 2011, overwrite it, or something else?

 

Also I have about 2 months remaining on the upgraded current active version 2011.  Assuming the new 2010 updates the active 2011 license, will it add the 60 remaining days to the one-year new license?

 

BTW, love the Norton products.  Used to use McAfee many years ago and had a problem.  I've bought Norton for at least 10 years now and never had any issues to speak of and love the rock-solid protection and continued improvements to the interface and updates..