Use a common place for default values
Currently the default value of many settings is used in the backend code that implements something, and is also in the text of the help message, and might be in other "front-end" validation code that runs when the settings are saved. Having a default setting (e.g. number) used literally in 3 different places leads to it getting out-of-sync when the default is changed.
Put all default values (and other "constants") into include files. Use the values from the include files everywhere. That way the system stays consistent when default values are changed.