Fee rates
The product models a marketplace's fee rates so it can estimate a cost before the marketplace reports one. Where a rate you have negotiated differs from the channel default, you can override it in settings.
An override carries its own start date, and that date can be in the past. Saving one re-estimates the orders it covers rather than only the orders that arrive next, so a backdated override will change figures you have already read. Each override also belongs to one marketplace, and it can either name a single kind of fee or stand in for all of them.
Scope
Whether this override replaces the marketplace default for every product you sell, or only for the one product shown.
An override changes estimates only. A settled fee is what the marketplace actually charged, and no override can move it.