From my friend Bernard on another pool forum, here's a trick to measure down to 10 ppm (and up to 150 ppm) CYA:
For the 30-100 ppm view tube (Taylor (9197): Mix 3.5 mL pool water and 3.5 mL CYA Standard Solution and proceed as usual, adding 7 mL R-0013, cap, mix and pour into the view tube.
If the dot disappears at 30 ppm, there's 10 ppm CYA in the pool water.
If the dot disappears at 100 ppm, you have 150 ppm CYA in the pool water.
In other words, dilute the CYA Standard Solution 1:1 with pool water and proceed with testing.
For the 20-100 ppm view tube (Taylor 9193): Use one quarter of Standard Solution and three quarters of pool water and proceed by adding your R-0013 etc.
If the dot disappears at 20 ppm, there's 10 ppm CYA in the pool water.