Recall that the table that had one variable had two rows because there are only two choices for the value of the variable.
The And table with two variables has four rows for this reason: For each literal value choice in the first column, I have two choices for the literal value in the second column. This means that when I select a literal value for a cell in the first column, I must use two rows to accommodate the literal values in the second column, thus two times two rows.
If I have three variables, then each row in the two variable table must be expanded to two rows; thus two times two times two rows for a total of eight rows.