It's not clear to me whether
dat "Hello"
is supposed to generate 5 words or 3 (with one byte of padding)
according to this pic it is one word per 8 bit character:
so
:data dat 0x170, "Hello ", 0x2e1 ...
will generate
0x0170 0x0048 0x0065 0x006c 0x006c 0x006f 0x0020 0x02e1
etc.
he tests the difference between normal chars and the special chars with
ifg a, 0xff
this would conclude that all ascii char will have its own word