Define Matlab code (FM demodulation)

fm circuits with matlab output

Hi, I have a matlab code here
it acquires FM modulated signal from sound card can perform FM demodulation
however, i don't why it set vcok (VCO K constant) at 0.176
anyone can explain to me how and why it is set to 0.176?

Fc = 2144; %select VCO carrier frequency
vcok = 0.176; %select vco constant
Fs = 40000; %select sound card sampling frequency
samptime = 3; %select sampling time (in seconds)
y = wavrecord(samptime*Fs, Fs, 'double'); %sample sound into y
wavplay(y, Fs); %play the recorded sound
x = (demod(y, Fc, Fs, 'fm', vcok)); %FM demodulate the sound
cutoff = 100/(Fs/2); %cutoff(1/2 sampling frequency)
[b, a] = butter(4,cutoff); %design butterworth low pass filter
xfilt = filter(b,a,x); %filter demodulation signal
time = 1/Fs1/Fs):samptime; %generate time vector
figure, plot(time,xfilt) %plot filtered data vs time
grid %overlay grid on plot
xlabel ('time ') %label x axis
ylabel ('input [volts]') %label y axis

thank you in advance