Renewal of Visa and interpretation of 'Valid Until'

I recently received back my passport after endorsement of it from PSB. It contains 02 written in 'Entries' (入境次数) field and 10 SEP 2013 as the date in 'Valid Untill' (有效期至) field. While in Remarks filed it is written as "Permitted to stay until 30 OCT 2013 for this time, and to stay for 42 days each time since the next entry". The officer told me that the validity of it is till 30 OCT 2013, but then I am really confused what is the purpose of 10 SEP 2013 written in 'Valid Untill' field? Does it corresponds to the entries i.e. the entries may be availed before this date?