At the moment, the app itself records cues in a certain sports match. It captures the information by updating through the UIStepper which will update the UILabel's to 1, 2, 3... etc.
However, when I press 'minus' on the UIStepper to change the UILabel back to zero, the UILabel on the right side of the UIStepper that shows the percentages of the cues displays 'nan%' Please see the attached picture.

Why does it do this?
Code for the percentage labels
self.smashPercentageLabel.text = [NSString stringWithFormat:@"%.2f%%",([self.smashLabel.text floatValue]/self.rallies)*100];
Thanks.