Ok..

Here's £1500 and if you stick we'll give you an extra £500.
Now, you can either take the £2000 or gamble for the jackpot.
You can gamble based on any month or months in the period April 2009 to March 2011 the dealer will select an equivalent number of random months to check.
If your total payment for all the months checked was lower than the actual figure for the period you get the difference and if the difference is over £750 you win the bonus £500 making a grand NHSBSA CIP jackpot of £2000 plus over £750 that should have been yours in the first place!
But if on the other hand your payment was higher than it should have been you will loose the difference as well as not getting the £500 bonus payment. You may end up having to pay back the £1500 from the bank.

What if they're the same I hear you ask... well there's nothing for a pair, not in this game!
So which is it to be, Higher or Lower!