The same meal, a different bill
Two restaurants may show the same menu price but produce different final bills after delivery and service charges. A trading chart also does not display every cost of a transaction. Today we separate the quoted spread, commission and the difference between requested and executed price. We are not searching for a magic setting; we are identifying the assumptions behind a reported result.
Buying and selling use different quotes
Imagine simultaneous quotes of one hundred for selling and one hundred and one for buying. The gap is one unit. An immediate purchase and sale with unchanged quotes is affected by that gap. Real instruments have specific quotation and charting conventions. A chart can display one price type while transactions use the appropriate bid or ask. Read the instrument specifications and test assumptions rather than guessing.
Example one: the round trip
Suppose a pre-cost result is twenty units. The round-trip commission is two units and an assumed slippage effect costs another two. Sixteen units remain. However, deducting these again is wrong when the report already includes them. Do not confuse a per-side fee with the full round-trip fee. These figures are teaching values, not a broker’s price list or actual BamaUp performance.
Slippage and delay are not identical
Slippage means execution differs from the intended price, and the difference is not always in the same direction. Delay is the time between a request and response or execution. One delay setting cannot guarantee a reconstruction of every liquidity condition or broker behavior. Around news or disconnection, inspect duplicate orders, sizing and exits as well as returns. Historical testing cannot guarantee every live operational outcome.
Example two: comparable scenarios
Define three runs: a baseline, higher costs and a different delay assumption. Hold the robot version, inputs and dates fixed, changing only the intended factor at each step. Retain unfavorable results. If a small cost change destroys the result, that deserves investigation, not another search for the prettiest screenshot. Document stress assumptions from relevant evidence rather than choosing them after seeing the outcome.
The practical assignment
Create a table containing the run name, included costs, delay assumption, net result and execution errors. For each expense, note whether it was already in the report or deducted separately. Our example left sixteen units. If the same four units had already been deducted, would you subtract them again? No. These four lessons establish foundations for further validation and demo practice, not permission to skip them.