Staking works like a lottery, the principle is the same with every PoS coin.
There is a minimum time that the coins need to be in your wallet, in this case 24hrs.
After that your weight will become important, that means the qty of coins that have the right to receive PoS. If your weight is one of the highest on that moment then there is a possibilty that you receive your PoS if there is no other with that same weight. That is why you get orphans sometimes. You don't need to worry with orphans, you will see that your wallet will receive an other stake (a little bit higher) for that orphand stake.