Code 39 barcodes often include a checksum character, which is not usually printed under the barcode. There is no way for the toolkit to determine whether the last character is a checksum or just part of the barcode string - and so all the characters are included in the string returned to the calling application.
The checksum for Code 39 barcodes is usually a mod-43 checksum worked out as follows:
Each character in the symbol set has a value. 0 = 0, 1 = 1,...., 9 = 9, A = 10,......, Z = 35, - = 36, . = 37, space = 38, $ = 39, / = 40, + = 41, % = 42.
Sum the values of the characters and take the remainder on division by 43. This is the value of the checksum.
