While looking at the 914 info (the link is at the top of the page) it shows under chassis numbers in 1970 that the production numbers were 4702900001 to 4702913312. That would make a total of 13,311 cars produced.
But if you go to the production link in the 914 info section it shows 20,241 cars produced that year.
Are there 6,930 brand new cars sitting in a lost warehouse somewhere?