Why does the State Patent Office issue two patent certificates for the same product?

The same product may contain many different technical improvements, and each technical improvement can apply for a patent.

For example, for a mobile phone, the structure of the mobile phone can be patented, the internal circuit that realizes a certain function of the mobile phone can be patented, and the new function of the mobile phone can also be patented, so that the same mobile phone can obtain different patent protection.