Where does the magic number/offset, 17.9, come from?

[anyou-jiang]

Hi, RuiMachado39, can you help explain how to get the magic number '17.9' in the following lines of code?

for i=1:size(startDensityCodeVector,2)
startDNL(i) = startDensityCodeVector(i)* binSize - 17.9;
startDNLLSB(i) = startDNL(i)/17.9;
end

for i=1:size(stopDensityCodeVector,2)
stopDNL(i) = stopDensityCodeVector(i)* binSize - 17.9;
stopDNLLSB(i) = stopDNL(i)/17.9;
end