24 hour care usually means 24 hour medical care. The money is to pay for nurses, medical machinery etc.
There is a defined math equation around life expectancy, multiplicands and the discount rate.
There is usually a general damages award (often a lump sum) for the actual one off injury and then special damages which takes account of future care needs, loss or earnings etc.
I suppose the thing I'm trying to say is that the figures might look huge but in reality they are calculated based on what the person 'needs' (not would like) and various experts on both sides of the table usually have to reach an agreement.