Well it is a feature request. Currently workrave works following way:

For example my Rest-brake is set to 5 min. Let assume that it is a time for my brake and Brake-screen appears. After 4:45 seconds I've decided to postpone or skip current brake which was almost done(15 seconds till the end of brake won't play the game) but the timer to the next brake is not resetted. It is still counting as I missed the brake. So I want to suggest to add "threshold" option for brake: so you can set the amount of time during the brake after which brake is considered completed. Correspondingly this should be reflected in statistics.