Try dragging the slider - the spin box will mirror its value too (and vice versa). Now, we preview your form to see how it would look in your application - press Ctrl + R or select Preview from the Form menu.
Repeat this process for the remaining spin boxes and sliders. Enter '255' for the maximum property as well. Then, click on the first vertical slider, you will see QAbstractSlider's properties. Within the Property Editor, you will see QSpinBox's properties.
