We would suggest to use the Auto Risk. Then it depends of the risk you take on the master trades, if you take a risk of 1% on the master side, you have to use the Auto Risk with a value of 1, if you risk 2% on the master and want to risk 1% on the slave, you have to set the Auto Risk with a value of 0.5.
With Auto Risk value, 1 will take the same risk, 2 twice the risk, 0.5 half the risk,...