Using 72 hr free transit policy, while still having 1 entry left in my double entry visa

I have a double entry visa for China.

After my first stay in China, I fly to Hong Kong. After a week in Hong Kong I fly back to Europe, but then I have an overnight layover in Xiamen, China, which has the 72 hours free transit policy.

I would like to use the 72 hours free transit for that short layover, and not the 2nd entry of my entry pemit.

The reason is, I am planning to make another trip to China later, still within the 3 months validity. So if I can, I like to keep the 2nd entry of my entry permit for later, and not waste it on this short transit.

Question: is that possible? And how do I prevent that the immigration officer automatically signs off the 2nd entry of my entry permit? Thanks for your advice.