If it earns 4% on float assuming 100% combined ratio, FRFHF should be earning around 900 million a year. At 6%, it will be 1.38 billion, at 8% it will be 1.84 billion.
Obviously the returns will be lumpy but I am talking of long term averages.
In 1997, Berkshire had 1.7% of market share for insurance float but held 25% of equities owned by the P&C Industry. So the quality of float matters, a lot!