The number of LifePoints (LP) is displayed on your dashboard prior to you clicking on the 'TAKE SURVEY' button.
The amount of the reward will vary depending on the length of the survey - the more time required on your part, the higher the amount of LP.
Please note: There is a slight delay of approximately 15 seconds for LP to be credited to your LP balance, once you complete a survey. You will see a circle rotating on the internet tab browser you are participating from, once it stops rotating, you should see the LP added to your balance.