Malware naming question

Hi,

How does the naming convention of Symantec malware signature work? Example:

Trojan.Gen and Trojan.Gen.2 Does this mean that Trojan.Gen.2 is a variation of the Trojan.Gen? I just wanna make sure, Also if someone from Symantec can answer this that would be better so we can guarantee that the answer is from Symantec. No disrespect to other users(I'm not a symantec employee either), I just wanna make it as official as possible.

Thank you,