Meizu M351 - Manual (Page 52)

Calculator
The calculator app lets you do basic operations, such as addition, subtraction,
multiplication, and division. Tap the Calculator icon on the Home screen to
launch the app.
c : Clear data.
: Tap to switch to scientific calculator; tap again to switch back'
: Tap to make the calculator floated above the home screen;
tap again to switch to the original mode.
App Guide 52