I read in the camaro white book that the last six digits in the VIN increase by 1 for each camaro built.. The last six in my Camaro's VIN is 516303... WTF?? werent there only 282,671 1979 Camaro's built?

Correct, but most years, Chevy started the Camaro VINs with 500,001, so that makes your Camaro #16,303 from that assembly plant. And, there will be another #16,303 Camaro in 1979 from the other assembly plant.