Spinners, or spin boxes, are used to specify values by typing or clicking the up or down arrows.   If you hover your mouse in between the up and down buttons you can click & drag to change the numerical values. The farther you drag the higher or lower the value changes.      

Hover with the curser between the two arrow head icons (up and down buttons).

When the curser changes to the Spinner Curser, left mouse-click and drag up or down to change the numerical values.

Tip provided by Richard Reilly, Graphic Designer and CorelDRAW Master.