When a usual 1-D barcode decoding fails, a 1-D barcode decoding using the second chance decode algorithm is executed if this checkbox is checked. The second chance decode algorithm is effective when the barcode that appears in the image is small or the 1-D barcode is not perpendicular to the camera optical axis. The chance of decoding a barcode improves if the "Use second chance decode" checkbox is checked, but the accuracy of decoding may deteriorate, sometimes resulting in a wrong string output.
Therefore, you have to be careful when enabling the "Use second chance decode" checkbox. "Use second chance decode" is available when [Barcode Type] is [Interleaved 2-of-5] or [Code 39] or [NW7 / Codabar].