Help with taxes and deductions (Beijing)

My offer for my post in Beijing has finally come through. Though I am pleased with the gross salary offered the estimated net figures quoted seem really low. I tried calculating everything myself, I used online calculators and I always keep getting higher net figures.

Can you please recommend someone that can help me see what the correct calculation should look like? Alternatively if any of you have a cool excel tool that will help me do that myself please send it over!

Thanks!