salifert phosphate

Hello i am fairly new to the hobby and started back in early June so my tank is about 4 months old. I was not happy with my nitrate levels so i started carbon dosing vodka to lower them and for around the first 3 weeks i was noticing them go down and then they did not seem to go down any more...

Ughhhhh. I kinda regret getting the Salifert Phosphate test kit. How the hell am I supposed to efficiently tell between 0.03 and 0.25. It is not too bad to tell that it is above 0.03, but that is where it becomes VERY difficult to read. I quadruple guess myself since at different angles/amounts...