stay for 4 days

Of course, you can. It is important that your stay is just 1 minute longer than 24 hours and up to 144 hours. In reality, beside this a "bit more than 24 hours", the main detail is your itinerary that has to be eligible for this visa free transit scheme. So, you should have an itinerary that involves three countries or eligible territories:

A country - B country (mainland China) - C country

And you should have in mind that you are allowed to have a landing just in one transit zone within mainland China being it Beijing, Shanghai, Guangdong province, Chengdu or some other...