What is Solid Ranking on Google

Curious! What I mean by solid. You must have heard ranking, but solid ranking, what is this?

I came across a surprising fact, I should not use surprising, because some of the SEO experts may know it, but for me it was surprising.

It all began, when I was checking the website ranking for one keyword i.e servo stabilizer on different computers. It was ranked at position 3 on some (also on some rank checking tools) – see image no. 1 position 9 on others and as per Google webmaster tool for 84 impressions in a day, position was 7.1 – see image no. 2

Image No. 1

Image No. 2