"This is a Sample and Hold device.
After you leave your sample,
please hold down the handle
until the contents have cleared".
As you may guess, the sign is on a toilet. One of those mandated "low flow" toilets, that borders on worse than useless. If you just flush it, like you would a normal toilet, it merely puts a small amount more water into the bowl. If all that you've done, is piss, I expect that it dilutes the mixture slightly. It certainly doesn't flush anything.
If you leave something more substantial, the only way to get anything to happen is to hold the handle down. Continuously. Until enough water dribbles into the bowl to instigate the siphon effect. This seems to take about 5 minutes, though it's probably closer to 45 seconds. Once you reach the critical level, the toilet usually flushes. That is if you haven't dropped a turd any more substantial than that a siamese cat might.
Drop a grogan that is actually worth the bother of dropping trou for, and you've got about a 20% chance that the toilet will just swirl your little turd sculpture around a bit, and it probably won't even go through the flush cycle, leaving the bowl full of both water and shit.
The piece of shit is supposed to be inside the bowl, not the bowl itself.