Submitted my thesis couple days back. When preparing slides for the defense, realized i made a calculation mistake in 2 out of the 4 chapters in the concentration of drug used. The results are not affected, just that i expressed the wrong concentration (quite a few; 0.6 instead of 0.3... things like that ) it has happened in 2 chapters.... My defense is next thursday followed by the viva..... i am freaking out if it is going affect my passing the PhD any difficult. I know that is the only mistake.... please advice guys....

It's not going to make the slightest bit of difference. They probably won't even notice. Just annotate this on your thesis copy that you take to your defence and if they mention it you can say you already know and will correct it.