4e4f6560_imator___MATLAB_mfilt_firdecim__Description
[Name] InputOffset [Values] Integers [Description] 
Contains a value derived from the number of input samples and the decimation factor — InputOffset = mod(length(nx),m) where nx is the number of input samples that have been processed so far and m is the decimation factor.
Direct-form FIR polyphase decimator - MATLAB mfilt.firdecim