[Exim] return value from "exim -R example.com"?

I checked the document, http://www.exim.org/exim-html-3.00/doc/html/spec.html,
and couldn't find an answer... and searched it for "return"...

If I invoke "exim -R example.com" to force delivery, what are the return
values?

I've been getting -1 on occasion, not sure what this means.

thanks!

Paul