Cave Exploration Rebate

if i get 1 lucky point for each draw (for every 50 explore) is it 20 draws for 100% chance to get the weekly jackpot or 21 draws

because on the Cave Exploration Rebate where it says about the lucky points it says have a full score to get a big reward the next time you draw is that saying get 20 lucky points and draw again to get a big reward or explore 2000 and then do a 50 explore draw again to get a big reward