You refer to some different version of the game. It looks totally different than we have at BGA.
The numbers near the icons (0,1,2,3) mean the initiative - the priority of your turn. The less - the earlier it will be played.
For example, player A plays Attack (2) and player B plays Heal (3). The player B gets damage and then restores HP.
Another example, player A plays Attack (2) and player B plays Block (1). The player B will not get any damage since the block is activated before the attack. And in this case, if playing Block (3, not 1) would allow player A to perform the attack successfully.