In my house, I have two buttons that I can use to flush my toilet. These buttons are labeled "Short Flush" and "Long Flush".
When pressing either of these and instantly letting go, the flush time is the same for either button. Even if I hold the button down until the sistern has completely emptied, the time it takes to re-fill it is the same no matter which button I press. Is there a logical reason for this? I can't figure out why separate buttons exist that do the same things - unless they actually both hit the same flush or similar (I'm not too confident in how these systems work)!