Try posting update again with correct chart (ignore previous chart).
One thing I have noticed is that since the indicator calculates Contango/Backwardation based on price close, the historical data will not show contango/backwardation high/low extremes Also, will not show backwardation at all, if that time frame did not close in backwardation. For instance, backwardation happens so fast you may need to a lower timeframe, for example 1 hour chart above shows XBTZ19 went into backwardation on July 16, 2019 and September 24, 2019.
This indicator will calculate in real time, but does not accurately show how high/low it got historically. I am working to hopefully fix this in version 2.0 which i have been working on. New version will show high and low for each candle. For instance, it will show on September 24th daily high for XBTZ19 contango was +272 and daily low was -172 backwardation. A 444 point swing in one day! However, it may take me a while to finalize version 2 so don't hold your breath.