Diagnostic output misses array length bytes when there are more than 1

[rvagg]

$ cborg hex2diag 970101010101010101010101010101010101010101010101 | head -2
97                                                # array(23)
  01                                              #   uint(1)
$ cborg hex2diag 9818010101010101010101010101010101010101010101010101 | head -2
98                                                # array(24)
  01                                              #   uint(1)

where's my missing second byte (0x18) to describe my >23 length array? it should look like this:

98 18                                             # array(24)
  01                                              #   uint(1)