Click distribution while split testing is not exact according to rotation weight?

Over a larger sample size, your landing page click distribution will become more and more exact.

Over a smaller sample size, it is more approximate in terms of rotation because we have hundreds of servers in all of the Amazon data centers.

For example, if a visitor comes to one server in California and another visitor comes to another server in New York, the servers are not syncing instantaneously to know which landing page was served exactly first.

So the number of clicks being somewhat off is due to the fact that we are trying to optimize speed and scale across many servers in all Amazon data centers.