When you collect enough 'tokens' to unlock a reward, you are then awarded the respective event reward and the required token amount is subtracted from your 'token total'.

Example: 

• The first event reward costs 25 tokens to unlock
• The second event reward costs 55 tokens to unlock

In order to unlock both these event rewards, your total amount of tokens collected needs to equal 80 or more. Each time the event repeats the previous token totals are reset. So if you had collected 100 tokens in the event last year, you would have 0 now.