Well using your example it would also depend on when he opened his wallet, if he opened on 3/24, all coins would stake and be paid around the same time.
People should also do the math to find out if they are up to date on minting. Example using 100,000:
20% of 100,000 is 20,000 (to be paid annually)
You are paid out every 20 days 365/20=18.25
20,000/18.25=1,095
1,095 is around the number you should receive every 20 days. Leave your wallet open 24 hrs at least.
For best results, it is best to keep the wallet open and minting at all times. For one thing, the sooner you mint the sooner you earn compound interest.