Once you have a pixel selection in place, it can be modified in several ways.
You can modify your pixel selection by enlarging or shrinking it, applying a feather to its edge, and/or by smoothing its curve. These options are available from the Selection menu as Grow/Shrink Selection, Feather Selection and Smooth Selection, respectively.
The following settings can be adjusted from the tool's context toolbar:
Circular—if this option is disabled (default), resizing honors the original selection shape. When enabled, the selection shape is made more rounded with increasing Radius values.
The following settings can be adjusted on the vertical slider:
Radius—controls the extent of the selection change. Negative values for Grow/Shrink will shrink the selection while positive values enlarge it.
You can modify your pixel selection by enlarging or shrinking it, applying a feather to its edge, and/or by smoothing its curve. These options are available from the Selection menu as Grow/Shrink Selection, Feather Selection and Smooth Selection, respectively.