Everything looks good.
On the linode itself, if you run "free -m" then you'll see what the machine is currently doing
eg on my linode
Code:
% free -m
total used free shared buffers cached
Mem: 1024 780 243 0 57 619
-/+ buffers/cache: 102 921
Swap: 256 0 256
Now the "Mem: free" value is memory that's not being used at all. In my case I have 240Mb of memory that's unused. If I cared then I could look to see if I have programs that peak to that usage or maybe I just have too much linode for my needs

The "Mem: cached" and the "buffers/cache free" value (921Mb) means that I have really don't have memory issues. Most of my RAM is used for I/O cache. That's the linux kernel remembering data that's already been read from disk so it doesn't need to hit the disk again.
Finally the "swap" row shows that my machine isn't going anywhere near the swap partition.
In your case you have a tiny tiny amount of swap in use. That could easily be the kernel deciding that some program really isn't likely to need the page of memory that it's claimed, so thrown it out to swap to make everything else even more efficient. 20bytes/s in I/O activity is close to zero, and can be ignored.
You're definitely not short of memory
