This is from the syslinux.doc file. The isolinux.doc and the website both state to use the syslinux.doc for information regarding the config file.
If flag_val is 0, display the boot: prompt only if the Shift or Alt
key is pressed, or Caps Lock or Scroll lock is set (this is the
default). If flag_val is 1, always display the boot: prompt.
Indicates how long to wait at the boot: prompt until booting
automatically, in units of 1/10 s. The timeout is cancelled as
soon as the user types anything on the keyboard, the assumption
being that the user will complete the command line already
begun. A timeout of zero will disable the timeout completely,
this is also the default.
NOTE: The maximum possible timeout value is 35996; corresponding to
just below one hour.
Download SysLinux from: http://www.kernel.org/pub/linux/utils/boot/syslinux
SysLinux web site: http://syslinux.zytor.com/index.php
Current version 2.02.
So to your question I would think you would want: