quantity and quote quantity. • When you buy 1 BTC at 19300, your average cost = 19300, base = 1, quote = -19300 • Then you sell 0.5 BTC at 20000, your average cost = 19300, base = 0.5, quote = -9300 • Then you buy 0.5 BTC at 18000, your average cost = 18650, base = 1, quote = -18300