_utmb and _utmz structure

Conversion University states that:
_utmz content is domainhash.timestamp.sessionnumber.campaignnumber.campaignparameters
and
_utmb content is domainhash plus "some additional values".
What are these values? When I've checked several sites, I found that they seem to look like uniquepagesnumber.10.beginningOfCurrentSession.
Not sure what this "10" is and when it changes.