CCA and Ah aren't necessarily related - although for any one type of battery they are.

Even within the various sub-types of basic lead-acid, there's big variations from car starter, through leisure and marine onto traction batteries - as the internal structure is different to give either good CCA for short periods, high Ah for long periods or compromises in between.

Gel batteries, which the Optima are, have a different construction to a lead-acid starter motor and are increasingly used as OE on cars with Stop-Start.