Sorry but I don't understand the word 'order' in this context if time plays no role. My simple problem is that I can't comprehend the spreads in the log of a back test. So I only want to know how to calculate the spread if time is 2018.02.23 21:59:14.915 and the .t1 file of the asset shows the entries above because my thinking of the spread as the difference of both absolut values at 2018.02.23 21:59:14.915 seems to be wrong.