The Indicative Index Value is a real-time feed of market data exclusive to the Nadex platform. Nadex members receive this live data at no charge, allowing them to view price history as well as the current price of Nadex contracts.
The Indicative price is a continuous moving average of the latest prices. This average is the same calculation used for the Nadex Expiration Value for the settlement of the Nadex contracts.
By using a moving average, Nadex can smooth out the price fluctuations and prevent a single anomalous execution from creating an unfair settlement at expiration. As a result, the price shown on the chart accurately reflects whether the contract would finish in the money or not.
For more detail, refer to Expiration Value