Traffic or Ranking Fluctuations?

Hi Guys,

So I have been working my bag of on my second amazon site for the past year (first site is sandboxed at the moment) and finally starting to get some consistent ranking this past week for one product page I have been targeting. I have been focusing on two keywords for this page (product name and product name review). I am ranking #6 for product name (14,800 exact per month) and #4 for product name review (1,000 exact per month). I have checked ranking several times a day for the past week using link assistant rank tracker, MS seo competition, and manually using google.com/ncr on a separate browser I never use and the rankings have been consistent.

The strange thing is the traffic for the two keywords seems to be all over the place even though the ranking seems the same. I get 20 to 60 uniques per day for a few days, then I had two days where I got 130 and 160 uniques and for the past two days is back to 20 to 40. I am wondering if this is just crazy traffic fluctuation or is the ranking of my keywords actually changing throughout the country even though they show the same for me when I check using the above mentioned methods. Thanks for any input.