Conflicting Test results for Nitrate.

Hey guys, its been quite a bit since I began dosing vodka. Ofcourse I am testing to see if my nitrates are going down.
I took some water to the LFS and He read less than 20 (API kit). I took the samples to 2 different LFS with similar results.
However, I am following the instructions on a new kit TO THE T, and I get different results. I even tried it with the LFS kit and I got more nitrates than he did.
Am I doing this wrong?
I have finished half the bottle of vodka and I dont seem to see any results. Unless I was right the first time and I had over 160nitrates... Since then I Halfed the feeding, removed fish, started vodka dosing and even added rock to the system.
I lost the color charts but im looking at pictures online and they're all kinda different in shades. I put the test tube in front of the screen so that light passes through it and the room is well lit. Im interpreting this somewhere between 30-60... (more?)

When the LFS does it, he gets 20 or below. The color is on the Yellow territory. Mine is always on the dark orange to red territory. Ill post pics.

Here is what I do:
I grab a bit of water from tank, wash the test tube.
Add the 5ml of water, meniscus right at the 5ml mark.
Shake bottle #1 well, and add 10 drops.
Cap it and mix for a bout 40 seconds
Shake bottle #2 for about a minute.
Add 10 drops of bottle 2 cap and shake test tube for 1 minute.
Usually color develops as im shaking, but I still wait about a minute before reading properly.
Doing something wrong here?
Either way, it feels like MAYBE the vodka MIGHT be reducing.. because before I was reading 160 as it was DARK RED, but it was so long ago i cant quite remember exactly. I still get quite the dark orange/red. Placing it in front of laptop screen (white background) it says its on the <40ish.
My doses are about 10mls of vodka a day (ish). (took about 2 months to get to the amount I am dosing). I know it's on the high dose but im being careful to add aeration and close monitoring. Skimmer definitely looks like its foaming a lot more too.

I wonder how long until I start getting yellows on the kit :S

 

Same test tube in both pics. One with notebook and the other in front of Laptop and color chart. Looks a bit different but you guys get the idea.
LFS gets a yellow tone to it. Definitely not this red/orange.

 

Get a salifert kit.