standard deviation (according to a site i use)

10. What is stdv (or standard deviation)?
Short Answer:
Basically it is a measure of variance. The bigger the stdv, the bigger your swings are.

Long Answer:
If you assume that your performance is normal (looks like a bell curve) then, 68% of your samples will fall within one standard deviation of the mean. About 95% will be within two standard deviations of the mean. For example, if your average hourly rate is +$10 and your standard deviation is ±$50, then 68% of your hours will be between -$40 and +$60 . Please Note: the stdv value in the charts is only an estimate of your "true" standard deviation. The more sessions you have, the more accurate this estimate should be. I use a weighted standard deviation, which means I take into account the length of the sessions when I calculate standard deviation. Also, as with all the statistics generated on this website, your past performance is NOT a guarantee of future performance. Future performance can be affected by other factors, including, but not limited to, changes in your playing style and that of your opponents.

But if its varience then id like someone like demi to explain and show what high and low rates of varience are.