If you are formatting your system due to finding the infections, that may be a bit extreme in my opinion. As for why there are entries found...there is no antivirus that can find 100% of infections 100% of the time. Every day there are many, many different variants of infections that are being made and until that new variant is reported and added to the software for detection, a virus can get in. Every antivirus does the best that it can with the information that it has on hand.