This is for the compression stack only, not rebound. and came from the instructions for a S2040 gold valve.

It assumes that you're using a gold valve and not the stock valve, although I expect (no evidence yet) that it only matters at high shaft rates. I understand that Showa forks have adequate flow for most purposes.
c30 c31 c32 c33 c34 c35 c36 c37 c38 c39
Gold valve goes here
.10 x 17 (1) .15 x 17 (2) .15 x 17 (3) .15 x 17 (4) .15 x 17 (5) .15 x 17 (6) .15 x 17 (7) .15 x 17 (8) .15 x 17 (9) .15 x 17
<----- .10 x 15 ----->
<----- .10 x 13 ----->
<----- .10 x 12 ----->
<----- .10 x 11 ----->
<----- .10 x 10 ----->
<----- .10 x 9 ----->

Here is the RaceTech chart for which shimstack to use.

They only list a single rebound stack in the S2040 instructions.

Gold Valve goes here
(6) .15 x 17
(1) .10 x 9
baseplate
This appears to be "r16".
See below to see if this makes sense for you.


FRGV S02 rebound info

This comes from the S02 rebound valve instructions:
r14 r15 r16 r17 r18 r19 r20 r21 r22 r23
(4) .15 x 17 (5) .15 x 17 (6) .15 x 17 (7) .15 x 17 (8) .15 x 17 (9) .15 x 17 (10) .15 x 17 (11) .15 x 17 (12) .15 x 17 (13) .15 x 17
<----- .10 x 9mm ----->
Start with r18. It's "perfect" for .90kg/mm springs, US-1 (15.2 cSt) oil, and 10mm diameter damper rods. Don't forget this is for 20mm cartridges.

from there:

+4 for springs between 1.05 and 1.1kg/mm
+2 for springs between .96 and 1.05kg/mm
no change for springs between .85 and .95 kg/mm
-2 for springs between .65 and .85kg/mm
-4 for springs between .55 and .65kg/mm

no change for 5 wt oil (US-1)
-2 for 10 wt (US-2) oil

+1 for 12mm damper rods (less oil being squished, so more dampign needed)