using a negative blocksize with "mke2fs", what should happen?

[Robert P. J. Day]

  just reading the man page for "mke2fs" and noticed, for the first
time, this about the "-b" blocksize option:

"If block-size is negative, then mke2fs will use hueristics [sic] to
determine the appropriate block size, with the constraint that the
block size will be at least block-size bytes.  This is use- ful for
certain hardware devices which require that the block- size be a
multiple of 2k."

  normally, if i ask for a blocksize of, say, 2047, mke2fs will round
down to the next lower valid blocksize of 1024.  but if i use -2047,
it should give me a blocksize of 2048?  it doesn't work that way, i
still get a blocksize of 1024.

  how should i interpret that statement in the man page?

rday