What is the cause of the error(unmarshal failed: toml: incomplete number) when running defualt toml?

[HanHoRang31]

When hugo server is commanded with example toml,
an error appears with the message
error "./config.toml:30:15": unmarshal failed: toml: incomplete numberunmarshal failed: toml: incomplete number

what is error?
:30:15 is defualt=auto

  [params.colorScheme]
    # Enable toggle colorScheme
    # Default to true
    toggle = true
    # Default colorScheme
    # Default to auto
    default = auto