Two genuinely different draw methods, not just a toggle

"No repeats" isn't a filter applied after the fact — it's a completely different drawing method. With repeats allowed, each number is drawn independently, so the exact same value can come up more than once, the same way rolling a die five times can land on the same number twice. With "no repeats" on, each draw removes that number from the available pool before the next draw, the same way drawing raffle tickets from a bag without putting them back guarantees a set of distinct numbers.

How often repeats sneak in when they're allowed

It's easy to underestimate how often a repeat shows up by chance in a small draw from a larger range. Draw 5 numbers between 1 and 100 with repeats allowed (the calculator's own default range and count), and there's roughly a 9.7% chance at least two of those five numbers match — nearly 1 in 10, even though the range is 100 wide and only 5 numbers are being drawn. That's the same birthday-paradox effect behind the famous "23 people in a room" coincidence: the chance of a match climbs much faster than intuition suggests once you're comparing every draw against every other draw, not just checking each one individually against a fixed target.