In terms of market theory, it would be a case of there are ~800k...

In terms of market theory, it would be a case of there are ~800k less shares on issue so your slice of the pie is greater. But since the company spent cash to buy them back, the pie itself is smaller.

In this case, the reduction in pie size is slightly greater than the increase in slice ratio due to the fact that the average price paid was higher than current share price so it should result in a minor drop. in theory.

In reality, it's a minor blip on the radar and probably doesn't even fall into an individual investors considerations, target price, and decision as to whether or not to buy in.