Parent classes sometimes contain multiple derived classes that might also be parent classes themselves.
If a document class is derived from one or more parent document classes, each event for that document classes also executes in all parent document classes, starting at the most senior parent class.
Both bottom up and top down apply to available events. For most users, the default setting of Top Down is the most appropriate.
Change the settings for Inheritance Chronology event sequences only if scripts exist for those events. Unless there is a lot of code, it is probably easier to change the code, rather than change the event chronology.