1) If you know the author of the code (includes yourself) and you know their comments are a good indication of the code, you just read them and move along. No need to understand what they do.
2) If you don't know the author or you know their comments are often out of date (which you can check with git blame but let's ignore that) the comments tells you what the original intention was, and with an already mental model its easier to read code and understand what it's doing, even if it contains mistakes (in the worst case the code will have nothing to do, so it will be like if you had no comment).
1) If you know the author of the code (includes yourself) and you know their comments are a good indication of the code, you just read them and move along. No need to understand what they do.
2) If you don't know the author or you know their comments are often out of date (which you can check with git blame but let's ignore that) the comments tells you what the original intention was, and with an already mental model its easier to read code and understand what it's doing, even if it contains mistakes (in the worst case the code will have nothing to do, so it will be like if you had no comment).