Various small bonusses can be added to a player when being build to give some variance as as the build method by injecting DNAs into a robot is a very complex construction - even though we are in the fourth millenium.

That is why they can increase with +1 in quality and sometimes even more when being built compared to what the quality says before clicking the build button.

You can boost these small bonusses when building by upgrading your robot constructor with your staff boosters.