When you hit a button, usually it switches back and forth a bunch of times as the two metal plates vibrate against one another. At 72MHz, youll need to watch out for this, for example:
int count = 0;
void loop() {
while(!digitalRead(BOARD_BUT_PIN)); // wait for press
// delay(1) // uncomment this line for simple solution
while(digitalRead(BOARD_BUT_PIN)); // wait for button up
count++;
}
this could easily result in a count of more than 1 despite only pressing and releasing the button once. A simple solution is to add a delay. But you can be more clever than that!
here is an article on the subject
http://www.eetimes.com/discussion/break-point/4024944/The-secret-life-of-switches