When you see
$this->bbcode_second_pass_code('', '
You must specify a boot entry to delete (see the -b option).
')
and also
$this->bbcode_second_pass_code('', '
-b | --bootnum XXXX modify BootXXXX (hex)
')
It means
$this->bbcode_second_pass_code('', '
-b | --bootnum XXXX BootXXXX (hex). Specify the bootnum to act on when using another option at the same time.
')