To make selections of a specified area size or smaller on an open design:
1. Open the Selection Menu
Choose the Selection Menu from the tool bar.
2. Choose Isolated Areas
From the drop down, select the 'Isolated Areas' option (the last one).
3. Define the Selection Area
On the popup dialog, type in the approximate size of the areas (in pixels) you would like to select.
Click 'OK' to confirm. All areas smaller than the specified area will be selected in the design.
4. Selection Area reference
To make easier estimations for defining selection area sizes, you can make a manual selection using the Magic Wand tool and refer to the total area of that selection.
First, choose the Magic Wand tool from the toolbar.
Now make a selection on the design that is roughly the size of the areas you want to select in the whole design.
The total area of the selection will be shown on the tool tip bar at the bottom. You can use this value while defining the area for Isolated Area selection (Step 3).
Additional info : The area is equivalent to the number of knots (or pixels) in the selection.