This is a feature aimed to take into account the position of a thumb on a page. Ie thumbs at the top of a page usually get more clicks then bottom ones. Thus to equalize their chances to get to the top we can apply Cell K to thumbs' CTR.

Here's an example:

Let's say we have a thumb A at the top gets 5 clicks and another one (B) at the bottom 2 clicks (let's add we had 10 views). CTR of the thumb A will be 5/10 = 0.5 , B - 2/10 = 0.2

But if we know the the one at the top is 5 times more likely to get a hit - we can apply this K and it's CTR will be 0.5 / 5 = 0.1 and this is a way for the thumb И to get to the top.

If you have enough traffic you can use “Recalculate Cell K, Recalculate Cell K each minute ” and script will try to figure out Cell K automatically. Or you can set it manually in Rotation - Cell K.