I'm guessing they're octal by some weird default. I was able to make similar output making up a dummy file using that presumption (entering his numbers using hexl-mode in emacs) that produced similar output on OS X with the default /usr/bin/hexdump. I'm partial to od -xa myself.

$ hexdump -c foo
0000000  \0  \0 001 257  \n 344  \0 003  \0  \0  \0   s  \0 006 002 26
+7
0000010
$ od -xa foo
0000000      0000    af01    e40a    0300    0000    7300    0600    b
+702
         nul nul soh  af  nl  e4 nul etx nul nul nul   s nul ack stx  
+b7
0000020
[download]

Edit: Derp, his \a should of course be 0x07 not \n / 0x0a. I need moar caffeine . . .