Charts in the trading terminal display the Bid price by default; however, not all positions are closed at this price.
Long positions (Buy) are opened at the Ask price and closed at the Bid price, while short positions (Sell) are opened at the Bid price and closed at the Ask price.
As a result, the chart shows only the Bid price, which is used to close long (Buy) positions.
You can enable the Ask line in the chart settings.