I'm wondering if the two statements given showing the index space size as described. I've the impression they show the space size of the tables.
"Each page is typically 8 kilobytes. (Remember, relpages is only updated by VACUUM, ANALYZE, and a few DDL commands such as CREATE INDEX.)"
So while it takes a bit of interpretation it is stated that "relpages" are not a size on their own but a value to be multiplied by 8k to come up with the disk size (typically since one can compile the server with a different page size).
