Pleading guilty means you yourself admit your guilt(often in exchange for some concession such as a reduced crime or reduced sentence.) This in contrast to a judge or jury finding you guilty. The latter is considered a "contested" case. Contested cases are what the US uses for the convictions rate percentage. The vast majority of federal criminal cases in the US are not contested and do not go to trial, despite what TV courtroom drama would have you believe. If you plead guilty, a conviction will still be entered I was just pointing out the procedural differences and how they are counted.

It includes cases where they plead guilty, it's not made from just them.