Do you mean how do you calculate the Compensation?
It's mad up of two elements: The first is dead simple and simply consists of the total of premium payments that you made.
The second is more complex as its 8% per annum for each premium for the length of time that the bank has held that premium.
This is explained (with some examples) on this page:
http://forums.moneysavingexpert.com/showthread.php?t=2697331
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