private void cancelTimer(final Widget sender) {
        if (sender == incrementArrow) {
            sender.getElement().setClassName("valueSpinner-arrow valueSpinner-arrowUp");
        } else {
            sender.getElement().setClassName("valueSpinner-arrow valueSpinner-arrowDown");
        }
        timer.cancel();
    }
Decreases the current value of the spinner by subtracting current step
stroom-core-client-widget/src/main/java/stroom/widget/valuespinner/client/Spinner.java