Questrade average cost calculation... Pls help

So I got 5 shares of company X @ $220/ea. Subsequently, the price dropped, and when it reached $180/ea, I got 5 more shares (10 in total so far). It then went back up to $220, and I sold 5 shares at $220/ea since I only wanted to keep 5 shares long term. I thought my average share price for the 5 shares in my portfolio was going to be $180/ea now, but Questrade is showing that I now have 5 shares at an average price of $200/ea (i.e. the average of the two orignial prices that I bought my shares at). That makes no sense at all. Is that a calculation mistake? Pls help me understand