For example, on the account of the trader there is $100. On your account there is $150. You can set reopening of lots with a ratio from 1:10 to 10:1 with any interval (2:3, 7:2,7:6, 9:1 etc. - any figures). At the same time at opening of the lot at the account of the trader, on your account is opened the transaction with lot equal to lot of the trader increase by a ratio.
I.e. If you set the ratio 3:2, then when opening by the trader of the transaction on 0.4 lots, you will get opened 0.4*3/2 = 0.6 Reopening by means of a ratio counts transaction lot in any other manner - when opening the transaction by the trader, the ratio of your equity and equity of the trader is considered. In this case 150/100. Transaction lot = the trader's lot * on a ratio of equity. In this case, if the trader opens the transaction on 0.6 lots, then you will open the transaction 0,6*150/100=0,9 lots.
At the same time, you can set in the ratio not all your equity, but a certain sum. For example on your account of $100, but you want to risk only $10. Then you set reopening based on the ratio of equity, and set your size of equity of equal $10. Then lot of the transaction will be equal to - lot of the trader multiply on $10 and divide into equity of the trader.
I.e. If he opened the transaction, it for some time was in a plus (for examle in plus for $200), and you closed it, and the trader closed it at the level of +100$, then you will pay the commission only from $100 (for example if the commission of the trader is 10%), you pay $10. At the same time, if you closed the transaction at a loss - you pay the commission from the level of profitability of the trader.