China 3 month multiple entry tourist visa - extension?

Hi, I have a 3 month multiple entry tourist visa. I first entered China on 27th July, so my visa would be expiring on 27th of this month (October). However I went to Philippines for the October holiday, so my ren-entry stamp in my passport is from just last week. Does that mean I got another 3 months from my re-entry? Or will I need to apply for an extension? I plan to stay in China until beginning of December.
Thanks for the help!