Any set of tiles revealed face-up on the table — whether called from a discard or shown voluntarily — is considered exposed for the rest of the hand.
Exposures are public: everyone at the table can see them and use that information to guess at your hand. Once a set is placed face-up, it can't be hidden again.
Example
A called Pung of 3 Dots sits in front of you, visible to every player, for the remainder of the hand.
