If you often encounter full or insufficient storage in your phone , please upgrade your firmware to the latest version for supporting this feature and to optimize the internal storage in a few seconds to the best condition and status. Please refer to（How to update firmware on my phone?）.
Firmware edition:
ZE550ML: V2.20.40.144(WW)
ZE551ML: V2.20.40.174(WW)/V2.20.40.174(JP)
ZX551ML: V2.26.40.52(WW)/V2.26.40.53(JP)/2.26.40.56(CN)
