The current version of the FIFO rule forbids two things: having orders of the same lot size and having orders in opposite directions. That's a bit simplified, but that's how it is. To have all orders of different lot sizes, you need to set the '2nd Trader Multiplier' to something which will give you the lot size of the second trade that is not the same as the first one. The value you need depends on the risks you use and your deposit size. If you use small risks on a small deposit, you may need 1.5 or even 2 to change from 0.01 lot to 0.02. If you have a big deposit size, even 1.1 will be enough to change, let's say, 0.1 to 0.11. To avoid orders in the opposite direction, you need to set the 'Allow Hedging' setting to false. This way, you won't have FIFO violations.