I'm trying to increase my understanding of calendar spread charts in IB. Any info/suggestions are appreciated, but I have two main questions: When charting such as in the screenshot, the candlesticks show long tails on both ends... is price fluctiating and orders being filled at these levels such as in standard candlestick charts, or are the tails representative of something else? Also, the charting options give me the choice of bid/ask or midpoint which essentially show the same image. What is the difference? Thanks for the clarification. Image attached.