Get yourself a better test kit (Taylor K-2006) and then use it to drop the TA to 70 ppm. You will find you have even better pH stability. Then use the Taylor kit to get the CYA to 80 ppm.
You just cannot do it with strips. They do not have the resolution and you inexpensive drop kit is not going to cut it either. I am going to guess it has a comparator for the chlorine test that has shades of yellow. Right?
If it does it only tests total chlorine, not free chloirne and combined chlorine, no matter what the instructions might say! OTO does not accurately measure FC.