Perhaps this will make it easier to understand:
A DC8 is configured just like a 707, 727, 737, 757, 319, 320...with one aisle running down the center of the cabin. It has many rows of seats and each row is split into two sections with the aisle as the dividing line between sections.
For example, when standing in the Coach cabin and facing the cockpit, you would have for Row 1 (left to right):
seats A,B,C then the aisle and then seats D,E,F.
Of course, this pattern is repeated for every row in the cabin.
A wide-body aircraft, such as the DC10, MD11, L-1011, 767, 747, 777, 300, 310, 330, 340 has two aisles running the length of the cabin. The aisles split each row of seats into three sections. For example, on an American Airlines DC10 or MD11 in Coach:
From left to right (facing the cockpit) you would have in Row 1:
seats A,B then an aisle, then seats C,D,E,F,G then another aisle then seats H,J.
Hope this further clarifies the matter.