Yup, exactly right: on the disc region mask for each allowed the bit is set to 0
e.g. regions 1,2,4 enabled:

8x654321  region
76543210  bit
11110100  = the decimal value reported in IFOedit of 244 (hex F4).

If you wanted to be l33t, load up VIDEO_TS.IFO or .BUP in your favorite hex editor and look up byte 23, the binary value there is the mask. 

Authoring software appears to be inconsistent as to what happens by default with bit 7 and 8 (based on what I've observed with examined commercial discs)... bit 7 was reserved but AFAIK never implemented in the spec, and 8 I recall being for international vessels (e.g. aircraft, cruise ships,... the ISS ) so can't really say if a consumer disc setting for bit 8 was actually a deliberate decision to restrict that sort of use or not.

Anyway... Profiler only tracks the lower 6 bits, so just looking at the decimal value can be a bit missleading with the two high bits being a free for all... "region free" for our purposes can be decimal 0, 64, 128 or 192 (and these options also skew the more restrictive readings.)

Fortunately, inspection software does all this work for you so all the above is just academic.