Storage types are going to be 8 or even 16-bit multiples because
of computer design. The only thing I would understand from a
storage type is that the actual data being stored is shorter or
equal to the data storage type length.

I don't know much about the numbers of graylevels acquired by
scanners. That's a separate question, and from looking at the
data, I would only be able to say that the number of bits
output from the ADC is between the size of the largest
integer stored and the storage type.

For questions about specific scanners, I'd ask your local people who
know the scanner, probably hardware people.

rich