I remember the first time I said that to Angel, she was only 2 years old. She couldn't speak a word and she could barely understand me. So along with hand gesture, I told her to wait on the baby chair while I ordered food at McDonald's.
I was worried that she might cry or try to climb off the chair, but she didn't. From afar I saw her kept looking at my direction, probably wondering when I would be back.
At 6 years old now, she still does that :) She put 100% trust on me, that's why I don't like to play pranks on her. And I always, always return to her as soon as possible.