The update increases the amount of microSD cards that are supported by the smartphone ZTE Axon 7
ZTE began distributing an updated version of the firmware for the smartphone Axon 7 (A2017U). B25 update not only fixes some bugs and optimizes the operation of the device, but adds some improvements.
In particular, it increases the maximum amount of microSD cards supported by the device, up to 256 GB.
Also, added Night Mode and the ability to disable some built-in applications, improves stability.
Source: GSM Arena