When Tinderbox creates a new document, it pre-configures all the System attributes and assigns each a default value (which can be a value of nothing/no value). If no other changes intervene, when a new note is added to the document, it directly inherits those values as the defaults of its own attributes.
The default values for each attribute data-type (e.g. String, Number, Date, etc.) are listed here.
Next in the cascade are config files…
See also—notes linking to here: