2020 Small Block Penalty Box Race Sign Up

so im a tad confused. So lets say the car runs 17.0 (random number), if it weighs more, it says add .1 per 100 pounds right? so wouldn't that make it 17.9? I probably have this backwards
I think all cars start with the nominal car, 318 2bb, 904, 2.76, 3300 lbs (without driver) at 15.9. If your car weighs 4200 lbs you would add .9 to the 15.9 for the weight putting you at 16.8 if all else was equal.