This test contains 72 pairs of letters or number, which are either same or different. If the pair is exactly the same, you are to mark the S box for that. If the pair is different in any way, you are to mark the D box.
Look at the examples given below. Mark an S box if both the parts of a pair are the same for that example. Mark the D box if the parts are different in any way.
Since in EXAMPLES V and W both parts of each pair were the same, you should have marked S box for these examples. In EXAMPLES U and X, the parts of each pair were different, so you should have marked the D box for these two examples.
The idea is to see how quickly and accurately you can decide whether pairs are the same or different, so work as quickly as you can without sacrificing the accuracy. If you are not sure of the right answer for a pair, mark the choice that is your best guess.