traveling to mainland China through Hong Kong with limited time left on my current Visa

I want to travel to mainland China and fly into Hong Kong from the USA I am a USA passport holder. I have a multiple entry 30 day type that is about to expire with 2 weeks left on it when I get to Hong Kong. Can I still use this before expiration or will I be denied and say I need to have more time left on my current one? I will only be staying or 1 week so I wont overstay at all.
Thanks
Pete