I've been intrigued about Shu Uemura's Face Architect Smoothing Fluid Foundation for a super l-o-n-g time. I've even gone to get my shade matched at the Shu counter but that's a story for another post. Lately I've been staring at the foundation shades offered online (again) but I've never been able to make any sense of it. I'm sure there are also Asia-only shades not shown online which annoys me to no end.
With all that said - Please don't be alarmed by what you are about to see next. I just had to do it to ease my troubled mind and to finally make some sense of those cryptic shade numbers! You can click on the pics to expand the diagrams and get a closer look.

Color Chart from Shu's USA website. Mine got flipped(sorry) - as the rows go from top to bottom they simultaneously progress from
dark
medium-dark
medium
light-medium
light

Color Chart modifed by yours truly. I ignored the number assigned to the shades, kept all the colors in their respective row but moved them around by the color I perceived.
Here's what I could sort out of the 3-digit numbers XYZ from the color charts:
Left digit X indicates how warm/pink or cool/yellow the shade is.
1 = warmest shade (most pink)
9 = coolest shade (most yellow)
Middle digit Y indicates how light or dark the shade is.
0 = darkest shade
8 = lightest shade
Right digit Z - I can't figure out. If you figure it out please let me know! There's only 4 or 5 and that's the extent of the range. Shade #164 and #165 are the only two shades that have the same XY digits and only the Z digit differs. They do appear to be different but I can't describe the distinction.
***** Update ***** Thanks to Anonymous for this extra confirmation! *****
"I have been to Shu counter,
It is correct that left digit X indicates how warm or cool the shade is. But the higher the number the warmer it will be. So no.9 is the warmest, most yellow of all. I have not seen no.1-3 but no. 5 is pinkish (in my opinion). No. 7 is equivalent to NC range in MAC. No. 9 is very yellow. 754 is a bit darker than NC35(I tried in the shop's light)."
***** 2nd Update *****
A fellow reader that is MAC NC20 was matched to shade #564 by an SA at the Shu Counter.