How are battery ratings used?

How are battery ratings used?
1.  Amp-Hour battery rating: This is the common rating of a battery. Amp-hour rating of battery capacity is calculated by multiplying the current (in amperes) by discharge time (in hours). Amp-hour battery rating is commonly when describing sealed lead acid batteries used in UPS systems, emergency lights and wheelchairs.
For example: a battery which delivers 2 amperes for 20 hours would have a 40 amp-hour battery rating (2 * 20= 40).
2.  Cold Cranking Amperage battery rating: CCA is the discharge load in amps which a battery can sustain for 30 seconds at 0 degrees F. and not fall below 1.2 volts per cell (7.2V on 12V battery). This rating measures a burst of energy that a car needs to start on a cold morning. This rating is used mainly for rating batteries for engine starting capacity and does not apply to NiCad batteries, NiMH batteries or alkaline batteries.
3.  Reserve capacity battery rating: RC is the number of minutes a new, fully charged battery at 80 degrees F. will sustain a discharge load of 25 amps to a cut-off voltage of 1.75 volts per cell (10.5V on 12V battery). This rating measures more of a continuous load on the battery.