Push for 5 seconds

This sign has been in a university bathroom (maybe all the bathrooms, I don't know) for months and I was never sure what it meant (click to enlarge). It looked like "5 seconds.....", but what is "Noolleo Ju Saey Yo"?
Yesterday, I was in the bathroom while a Korean English teacher was also there. I asked him about the sign. He said, "Push for five seconds". All I could think about was straining to pee faster. Who goes to the bathroom that fast? I think you would do yourself injury.

It was only after he had finished his job and held the flush mechanism, that he said, "hold this for five seconds". That made a lot more sense. Korean bathrooms often have stronger odours because few Koreans do flush the urinals.