For example, say I buy one contract at 1 and one at 3. NT will correctly display an average price of 2. If I then sell one of the contracts at 4, the price will not update to reflect my new average cost of 3. Furthermore, at a price of 3, NT will tell me that I'm one point in the money, when in fact I'm only at break-even.
If you add to and reduce a position multiple times, these inaccuracies eventually add up and make the numbers given by charttrader useless.
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