Hey Tia,
It is a bit difficult to give you an answer to that one really simply beacuse everyone is different hence cambridge say average losses are an average of stone a month. Men often tend to lose more quickly than us ladies but saying that there are some women that lose more too - there is a lady TTey who posts on minimins who lost 5 stone in 10 weeks whereas in the same timeframe I lost 2st 12lb which I was overjoyed with as I know I could not achieve that kind of loss on any other coventional diet. As for those that lose less than a stone a month - I'm sure there must be people out there that may have slower than average losses, for whatever reason, but most folks I have seen on minimins who are sticking to SS seem to achieve the stone a month.
Sorry I can't give you a more definitive answer - hopefully the prospect of an average stone a month will be enough to keep you motivated.