Sampey, when I trade BTC/USD and I want to sell BTC high (PING) and rebuy it back low (PONG), then my win is in BTC, e.g. I sell 1BTC for 1000 and when it falls I rebuy 2BTC at 500, therefore my gain would be 1BTC.
However, the "cumulative gain" shows the result in USD instead of BTC.
Any market on any exchange is expressed as 2 Currency :
The Market Currency : is the currency you define by the value QTY
The Partner Currency : is the currency you use to define the price (and the total value QTY x PRICE).
Gains are expressed as PARTNER Currency. I can express also gain is Market currency, i have no problems about that.
BUT at GLOBAL Exchange level, i have no way to express a global gain as Market Currency but only at Partner Currency.
I mean :
if you trade on
BTC/LTC
and
BTC/XRP
As single market level i can express your gain as BTC or LTC
But at global market level i must group the gain to the common currency, that is the partner currency. In this case BTC.