The left side of the display shows the file entries in terms of their:
The right side of the display shows some details about the first duplicate that was found for this particular left side file.
It is possible that the left file has more than one duplicate, the display shows us only one of its duplicates on the right.
Since I requested the duplicate check to be master with master, and I requested an all file display, then a given file can appear on both the left and right sides.
Each file will appear once and only once on the left side, but the file can appear on the right side possibly more than once.
A file appears on the right side if the left file has a duplicate, then the duplicate with the lowest index will be shown on the right side.
In the following screenshot, I pressed the column header for the Hash field. Pressing any column header causes the program to redisplay the data with the lines sorted by the selected column. Press again for a reverse sorted display.