Hungry Slime can be removed by matching blocks that the Hungry Slime is on, or by blowing up Items.
If the Hungry Slime isn't removed, it will move closer to the Apples outside the board one unit at a time, every turn, with negative numbers indicating turns marked on the Apples.
Once the Hungry Slime reaches the Apple, the amount of turns indicated on the Apple will be subtracted from your play turn.