He didn't exactly say ~that~. I think he said "first 200,000 GM vehicles will be eligible for *a* tax credit", & the Volt will qualify for the highest amount ($7500), and all of the "Gen 1" Volts should get a credit." What I took that to mean is that 200,000 GM rebates should be enough to cover all the "gen 1 Volts" and any other cars they make that qualify for some sort of credit.
I don't think he said specifically that 200,000 Volts will get the credit.