Click the Zoom Buttons or press Control – or Control + to operate.
The Zoom Buttons can be used to decrease or increase the magnification of the image in the Preview Viewport to the next programmed step.
If the current zoom value is between two steps, it will be increased or decreased to the next available step.
For example, if the current zoom value is 60%, pressing the [+] button will increase the zoom value to 66.67% which is the next step. Pressing the [+] button again will increase the zoom value to 100%.