How much does the rating for a single game mean?

So I have been here for a month haven't played a game of chess for like 30 years. Quite fun really but I wish I could learn not to blunder so much! Like every second game there is a blunder or two.

So my rating is going up and down like a roller coaster. At first I din't spend that much time in the analyze game part but the latest couple of days I had a look on that. My accuracy is all over the place, from like 50 to the top one that was 93 per cent. And highest rating for a game so far is 1400 if I remember correctly.

So what does that 1400 mean and any tips for not making all does blunders? I only play rapid, tried blitz and that pace was way out of my league.

Edit: The title of this post doesn't make sense but I can't seem to edit it...

Your rapid rating has settled down at 532, which actually isn't far below the site average.

Those single game ratings don't really count for much.