I dont understand why you should make it into 2 pool, you can make it to 1-20 just in one pool so people will not confuse about it. And I think the prize is low compare to the ticket price 0.002. the chance to win is only 10% on each number. May be you can consider about the prize later
Ok maybe a good idea to do 1 pool only 1 - 20 and of course then price will go up.
I think I will do this now, the one who wanted number 6 did not paid so can delete this one.
What do I mean is if we choose only one number the minimal prize should around 90% more and if you choose more then the prize will be lower because the chance is higher so you should make it lower so everyone will have the same chance to win that amount. If all numbers is filled you must get 0.04 mean while the total prize is only 0.035 so you still get some profit 0.005. I dont bother this but at least you can make this equal to eveyone else