In reality very little; it is more a measure of your potential. However, it wasn't a waste of time as you should now know your max HR and your LT from the plots made during the exam. Your lactate threshold (LT) is a number you can use in your training. It is much better to make training zones off a % of LT than a % of max HR. However, unlike training with max HR your zones can be over 100% (intervals).