[exim-dev] MAX_LOCALHOST_NUMBER and LOCALHOST_MAX

I have been reading about exim message ids (for enhancement
https://bugs.exim.org/show_bug.cgi?id=2956
).

I see that the code has both

src/config.h.defaults:#define MAX_LOCALHOST_NUMBER        256

and

src/exim.h-#if BASE_62 == 62
src/exim.h:# define LOCALHOST_MAX 16
src/exim.h-#else
src/exim.h:# define LOCALHOST_MAX 10
src/exim.h-#endif

Am I right in thinking that these are both for the config option
"localhost_number" ?
If so, is the max 256 or 16/10 ?

(16/10 means 16 on caseful filesystems, 10 on case-ignoring filesystems.)

Thanks,

-- 
Andrew C. Aitchison                      Kendal, UK
                    andrew@???