In this game you press X to confirm (move to next stuff). When the dogs pass in the screen you can press Space to increase the counter by 1.
In the end (after the dogs passed) it displays the number you counted (you can press backspace to delete and write your own number), so when you press X you're confirming the number. If you get it right, you go to the next level. If you're not right, you loose a life each time you press X.
Hope it helps.
The interface is a bit tricky... I mean, it's not obvious... Why X? Wouldn't Space be enough to confirm?
When you ask people to press some key, it's good to know what the action implies: "Press X to continue" or "Press X to confirm"/"Press Space to count dogs"/"Press X to show doggy style"
It's actually enjoyable for a while (before your head starts to hurt).