Unclear instructions.

Step 1 says to use x40 screws. Has a picture in the top right corner pointing out 3 holes of note on the drawer runners & there's only 2 pre made holes in the side panel. 
5 runners per side panel & 2 pre made holes for each runner = 10 screws per side panel. There are 2 panels so that only makes up 20 screws. If I need to put another 2 screws in somewhere a) why isn't there any pre made holes & b) why does it only point out 3 holes per runner and not 4? 

Pictures aren't clear where they want the screws to go. I'm contacting customer support tomorrow.