MATLAB function fixdt() question
While this is a marginally EE question since simulation of fixed-point algorithms is crucial to a lot of signal processing and control firmware development, you should be able to find this easily in the MATLAB documentation. 

The representation is as follows: 

\$RealWorldValue = StoredInteger \times 2^{-FractionLength}\$

If FractionLength = 26 and word length = 16 and StoredInteger = 32767, then the RealWorldValue is 0.00048826634884 (the maximum value that can be represented).

You can think of the FractionLength as an exponent, but one that is implied and not part of the variable.