I think the codes are put in as follows, if the code is 2358, you press the corresponding preset number that many times.
Like, for the first digit (2) press the preset 1 twice. For the second digit (3), press preset 2 three times, for the third digit (5), press the preset 3 five times, and for the last digit (8), press preset 4 eight times!!
Code digit Preset number on stereo
2 = 11
3 = 222
5 = 33333
8 = 44444444