There are no stupid questions. We all had to learn sometime.
The WS is the side that is often the inside or the back of something. If you're doing a stitch that is reversible you can just choose the side that you like best. If it matters you can put a pin or removable marker on the RS so you'll always know.
If you start the 4 rows on the RS then yes the last row would be a WS row. They are just clarifying that is where you are.