in the AssetsIB.csv provided with Zorro installation we have the following line

AUD/USD,0.77311,0.00005,0,0,0.0001,2.2,0,33,25000,0.5,

commission = 0.5

on interactive brokers website I read the following

IBKR offers competitive commissions on Forex, starting at 0.20 basis point * trade value, with a minimum of 2.00 USD (or USD currency equivalent) per order.

Questions --
1) is your 0.5 just a made up value ?
2) how can I express the "0.20 basis point * trade value with a minimum of 2.00 USD" concept in asset list commission field ?

thanks

The commission for Fx is per 10,000 contracts. I am not sure what "basis point * trade value" means, but would interpret it as 0.0001 multiplicated with the contract volume. When commision is calculated with a complex formula, as with IB, you have the choice between either using a simplified average commission, here probably the 0.5, or calculate the real commission value by script. In that case set the Commission variable to the calculated roundtrip value per 10,000 contracts before entering the trade.