As far as I can tell, the testing bodies use various algorithms to determine what clade you are in, trying to impute from SSRs what your SNPs might be - and the algorithms differ between providers. On the web you can find some standard 12 marker descriptions of what, say, a E3b#2 should look like - see http://freepages.genealogy.rootsweb.com/~gallgaedhil/haplo_e3b.htm
Theres a website that will estimate it for you - you just feed in your markers and it gives you the estimated haplogroup.
If you dont closely match one of these standards - then its almost guesswork putting you in a cluster.
If you are really interested then you should get a deep subclade test to prove what your SNPs really are.http://www.ystr.org/index.html
is a good place to see the geographic distribution of various haplotypes. There are also a lot of pie charts of their distribution scattered around the web