I filled amended tax return 1040x w/8936 for qualified plug in electric drive motor vehicle credit. I received back the 1040x w/8090-a asking to support line 7 on 8936

Any idea how to support line 7 on 8936 for for qualified plug in vehicle? I have included the amount of battery capacity  kilowatt hours which is 8.8 for Prius primes. Also, the 8009-a requires me to return Cp08 what does that mean?