.028

It is probably the size of the string, which corresponds to its diameter in inches (or millimeters in some cases). A folk guitar string bought individually with a draw of 0.28 corresponds to a string with a diameter of 0.028 inches (about 0.71 millimeters).

The draw of a string is the tension exerted on the string, which affects the playing sensation and the sound produced. Folk guitar strings are generally available in a variety of gauges, ranging from the lightest (.010 inches / .25 millimeters) to the heaviest (.013 inches / .33 millimeters). The higher the draw, the greater the tension exerted on the string, which can result in a more powerful and brilliant sound, but can also be more difficult to play for beginners or players with lower pressure strength.