Some Events give you the ability to trade in any leftover points for resources. You are only able to do so once you have claimed all the prizes you are able to first.  If you have enough points to claim any of the remaining prizes (excluding ones you have already claimed of course) you will need to claim as many as you can before you will be able to exchange whatever is left over for resources.  Once there are no more prizes left that you are able to claim with your remaining points you should have no issues exchanging your points for resources.