What is the assumed commission in equity graph?

Is there some text explaining what the default commission per trade for stocks, options, futures, and forex is? Is it fixed amount per trade, or fixed unit price per share of stock/contract/mini-lot?

Also, the “best case, no commis” and “best case, with commis” options in the equity graph yield the same graph, while the “realism adjusted, no commis” and “realism adjusted, with commis” options yield drastically different graphs for a stock system that averages 4 trades a day, indicating that commis are not zero in this case, so I think it may be a bug that commis in the best case option aren’t showing correctly? Thanks.