This chart is the same as the one you used in STEP 3-2.
You need to think of a way to convey the information of 2 squares as one single character.
Recall what you had to do to decode the information from your partner in STEP 3-2.
Just like you did in STEP 3-2, you have to flip the two letters to get the correct two-letter combination. After flipping them, is there a way to combine the 2-letter combinations to form one character?
For example, the letters "FI" and "VE" when combined can be expressed as a single number: "5".