injecting co2?

So i started to test my KH just now and i have added the maximum it shows on the chart (12 drops) and i stiil was stuck with a yellow color.I decided to test my snail tank which i add baking soda and crushed coral to and it turned blue on the first drop.I read the chart for 0*-3* and it says "discus,arowana,elephantnose,neons,cardinals and liveplants.
How could this be since i add all these things to the water.For snails it says my KH should be 8*-12*.Now back to the tank in question.I have already added the maximum drops so is it safe to assume i have no KH?or is it so high that 12 drops isn't enough?i highly doubt this since i add nothing to this tank compared to my snail tank which came out so low anyways
 
What brand of test kit are you using? I've been using the API brand kh/gh kit and its accurate enough for me.
 
I made a mistake, my test kit is produced by Hagen. Maybe a bad kit?
 
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