It’s the percentile method. Let’s assume you got 140 out of 200 in your 1st shift bringing you a percentile of 99.3 and your friend was in 2nd shift scoring 126 and a percentile 99.4. Here percentile means you have scored greater than what percentage of people. You having a percentile of 99.3 means you have scored higher than 99.3% candidates.

Now by rules your friend will get a lower rank because his percentile is higher although his marks are less than you. The percentile depends on the toppers marks in that shift. 

Hope I have cleared your doubts.