From the Super Mario Wiki
The Sluggish 'Shroom Orb
The Slow 'Shroom Orb (Sluggish 'Shroom Orb in Mario Party 6) is an orb in both Mario Party 6 and Mario Party 7. When used, it slows down the speed of the Dice Block tremendously, allowing players to choose the number they roll. Players do this by hitting when the number below the desired outcome is shown on the Dice Block; if a player wants to get a three, then the player is to hit when the Dice Block shows a two. They are one of the few Orbs used in the Solo Mode in Mario Party 6.