Commission table and tiers

I have 2 questions regarding AA commission settings, and a possible bug report.

Background:

  • I am using Amibroker 6.28
  • IB offers a tiered commission schedule. For futures in US, the table starts as this:
    <= 1000 Contracts - $0.85 p/ contract
    1001 .. 10000 - $0.65 p/ contract

First question: Is the following correct ?

For tier 1:
Tier Unit - shares
Tier Minimum - 1
Tier Maximum - 1000
....
For tier 2:
Tier Unit - shares
Tier Minimum - 1001
Tier Maximum - 10000
...

Second question:
IB says that the counter (number of contracts) is reset every month. Does Amibroker resets the tier counter every month during backtest (say, from-to range is 3 years) ?

Finally, I suspect this is a bug:
On AA windows there is a "save" button. The file it creates has all information on AA settings window, except the commission table.
How to reproduce:
1 - Enter some data on commission table
2 - Save AA settings to some file
3 - Make some change on commission table
4 - Reload the file you created on (2)

The result is that the commission table does not change back to what you put on (1).
If this is not a bug, it is very annoying. Consider 2 commission tables: one for futures and one for stocks.

  • The commission table cannot be set by AFL, and it cannot be loaded from a file....
  • You want to backtest a future, and next a stock.

I believe that the commission tiers are evaluated on a per trade basis. See this sentence in the documentation for the Commission Window:

There are 5 tiers of commission schedule table plus "default" tier that is used when others are not defined or transaction does not match any tier defined.

Because of that, there is no concept of a "reset". In your example, you would need a single trade of at least 1001 shares/contracts to be charged $0.65/contract. If the next trade was only 500 shares/contracts, then you would be charged $0.85/contract for that trade.