You're right!
I misread the line. Putting the commas in yes it should be another .3 deduction on the index.
That's probably out of reach on street tires...
So that would make my car's index 12.8 seconds.
Be interesting to take a pass with the shorter and stickier road race tires. No water, no burnout. Just clean them and pull up - same as I do on the street tires.