After Voile gave Celes the go ahead, the gambler explains the rules in a timely manner, teaching her about the types of hands you can have, what beats what, basic rules, and the like. Of course they need to show each other their hands to explain, but it wasn't a real game so it doesn't actually count. Once the practice game's over, she goes into further depth by taking the deck apart and going over things in a more detailed explanation.

Finally, when she's done listening to the sound of her own perfect voice explaining, she tilts her head and looks curiously at Voile. "Did you find my explanation sufficient?"

If nothing else, it was pretty thorough.