 The decode table has 15 entries because the symbols with two wide bars (1, 4 and 5) are listed twice.Assuming narrow elements are one unit wide and wide elements are two units, the average digit is 7.8 units.This is better than codes with a larger repertoire like Codabar (10 units) or Code 39 (11 units), but not quite as good as interleaved 2 of 5 (7 units).