order/tradingfees: correct fixed rate parts per _billion_ comment
@@ -57,7 +57,7 @@ func (f FixedRatePremium) LumpSumPremium(amt btcutil.Amount,
// PerBlockPremium calculates the absolute premium in fractions of satoshis for
// a one block duration from the amount and the specified fee rate in parts per
-// million.
+// billion.
func PerBlockPremium(amt btcutil.Amount, fixedRate uint32) float64 {
return float64(amt) * float64(fixedRate) / FeeRateTotalParts
}
