You have two choices here. If you choose "Sum " then Datasqueeze will integrate over the dependent variable. That is, for each value of the independent variable (say, Q) it will add up the values of all pixels between Q and Q + delta Q and inside the range of the dependent variable (say, Chi) chosen. If you choose "Average " then the program will plot the average counts/pixel over the same data range. This gives something more closely resembling the results of a measurement with a one-dimensional detector (e.g., a triple-axis diffractometer) in which a 1/Q Lorentz factor is applied to the data. In most cases the Average option is probably preferred, since it tends to reduce the non-statistical noise due to pixelation errors.