Puzzle rating is a separate thing.
You gain and/or lose rating points by playing rated games against other players, online, not bots.
My rating against bots
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Your rating is a provisional one which you get when you start your account.
Puzzle rating is a separate thing.
You gain and/or lose rating points by playing rated games against other players, online, not bots.
Puzzle rating is a separate thing.
You gain and/or lose rating points by playing rated games against other players, online, not bots.
The probable explanation is that you've ticked intermediate checkbox when starting out (depending on your answer you start with 400,800,1 200, 1 600, or 2 000 rating). This gives you starting ratings of 1 200. When you play against bots, your highest rating is displayed I believe. So because you haven't played a single game, your starting rating of 1 200 is displayed.
If you play some games and for instance acquire 1300 rapid rating, that rating will be displayed.
But you can't gain or lose rating points by playing bots. You gain and lose points by playing rated games against other people.
I see. Thank you. 
When I play against bots, it says (1200) next to my alias under the chessboard. I have two questions regarding this:
1. Where does that rating come from? On my profile it currently says that my rating is 1000, which is a rating I have reached by solving puzzles. Why am I given a higher rating when I play against bots?
2. Will it ever change? My "against bots" rating has been 1200 for a long time now. I've won several games against 1300-rated bots but my rating stays at 1200. I've also lost several games against 1300-bots, but I think my win/lose ratio should award me a higher rating soon. (When playing against bots, that is.) (I have also won a few games against bots rated higher than 1300.)
My plan is to play against 1300-bots until my own rating is increased to 1300, and then start playing against higher rated bots until I get a higher rating again. And so on. But my rating just stays the same.