At 13:12 of the third period in the Predators/Penguins game, Nashville requested a Coach's Challenge to review whether Matt Cullen was offside prior to Pittsburgh's goal.
After NHL Hockey Operations staff and the Linesmen reviewed all available replays, it was determined that Cullen preceded the puck into the attacking zone, causing an offside.
Therefore the original call is overturned - no goal Pittsburgh Penguins.
The clock is re-set to show 13:20 (6:40 elapsed time), when the off-side infraction occurred.
Since the Coach's Challenge resulted in the original call being overturned, the Predators retain their time-out.