What's in a number?

German broadband contender United Internet today reported Q2 results, and while we still have no VoIP subscriber numbers, the company now claims to be invoicing 100m minutes per month. Actually, the long form of the report states that 90m minutes were generated in June, so this marks a pretty strong volume growth rate. This is pure back-of-the-envelope stuff, but assuming that usage per sub is in line with PSTN voice usage in Europe (let's say 8 minutes per day), I think this 100m minute figure could imply a user base of around 420k.