Any CYA measurement at _5, we round up to the next 10. So consider that your CYA is 40.
We do that because the scale on cya is logatrithmic, not linear. You can see that the gradations between numbers in the vial are not evenly spaced. So halfway between numbers is closer to the higher number.
We do that because the scale on cya is logatrithmic, not linear. You can see that the gradations between numbers in the vial are not evenly spaced. So halfway between numbers is closer to the higher number.