TUNE HELP

[PepsiMan625]

I’m currently tuning some cars. I’m completely brand new. I don’t understand how I can accurately get the desired HP number I want without going over or under, surely there has to be a way to be exact? Also can you add KERS to any car if you copy and paste it from other cars? It doesn’t seem to be working for me but I could be missing something. If not, how do I add KERS to other cars? Thanks