Tax return question....?

So I filed my taxes a few weeks back, and got my refund just very recently.

When I filed it, I was expecting a very paltry amount in terms of a refund, ~$136...yet, to my wonderment my return was about 8x what I expected...

Should I be afraid? is CRA going to want this money back, or did they adjust it correctly? My taxes weren't the least bit complex, so I have to wonder about the margin of error here....

Thanks!