I see a new icon in the Pet RescueSage. A bomb with a number in it. What is this used for?

Faye_Barlow

New Bomb icon on Pet Sage with a number  in it. How do I use this? New Bomb icon on Pet Sage with a number  in it. How do I use this? New Bomb icon on Pet Sage with a number  in it. How do I use this? New Bomb icon on Pet Sage with a number  in it. How do I use this?

Thistle

The bomb with the countdown number is activated when any block touching it is cleared.