I think I've got this figured out.
Mick: yes, it's gonna be the tuning you said.
I don't think it's or 2 different instruments.
Also, i see that the designations 6th, 4th, etc are printed on teh envelopes; the D=Bb, X=F, etc is extra info affixed with stickers, possibly not by the manufacturer.
here's what it is:
The 6th string is the gauge of a normal D sting, but it's gonna only be tuned up to a Bb. Thus: 6th D=Bb. (It's a thin string too; the eye test says it's about a normal D, clearly not a low E.)
The 4th string will be what is normally a B/2nd string, but only tuned up to a G#, thus 4th B=G#. It explains the plain 4th string.
It also explains the X=F, as this set's 6th string is a normal 4th string; 5th is normal 3rd (we assume), 4th is normal 2nd, 3rd is normal 1st; the 2nd and 1st strings for this set have no corresponding "normal" string. So I guess the 5th string would say 5th G=D# (Eb) and 1st string would say 1st X=A# (Bb).
Solution to the puzzle is:
6th D=Bb
5th G=D#
4th B=G#
3rd E=C#
2nd X=F
1st X=Bb

(Sorry to mix sharps & flats; I'm going with how it's printed on the stickers.)

Get it?
Seriously, sorry so to waste anyone's time with this little oddity. Thanks for the replies. (It was drivin' me nuts for a few minutes!)
Best,
CC