"shared_buffers" and "temp_buffers" why manual and code are different?

Hi,

I want to tune the memory usage of PG (9.3.1) on my environment. I'm really
confused by the following two configuration parameters,

shared_buffers,
temp_buffers,

Take "shared_buffers" as the example, the manual says,

"Sets the amount of memory the database server uses for shared memory
buffers. The default is typically 128 megabytes (128MB), .... This setting
must be at least 128 kilobytes. "

However, when I look at the configuration code (below), the code shows it
should be the number of shared memory buffers *NOT* the size of the buffer
.

/* guc.c */
1638 {"shared_buffers", PGC_POSTMASTER, RESOURCES_MEM,
1639 gettext_noop("Sets the number of shared memory buffers
used by the server."),
1640 NULL,
1641 GUC_UNIT_BLOCKS
1642 },
1643 &NBuffers,
1644 1024, 16, INT_MAX / 2,
1645 NULL, NULL, NULL

So which one is correct?

Also, what exactly is the default value? The manual says that the default
is 128MB while the min is 128KB. But from the code, you can clearly see
that it's not the case.

Thank you very much!

Best regards,
Tianyin

--
Tianyin XU,
http://cseweb.ucsd.edu/~tixu/