Why do I get refunds?

Simpler than that: Giveaway was deleted! You can check which one here

From the FAQ

How many points (P) can I receive?

You will stop receiving points once you reach the maximum of 400 points. At that time, you will need to spend your points on giveaways before receiving more. In the below situations you might exceed the maximum point value.

1. You manually remove a giveaway entry, and points are refunded.
2. A giveaway you entered has been deleted. When this occurs, all users that joined the giveaway will have their points refunded.
3. You win a game while having other active giveaway entries for that same game. In this case the site will automatically remove those entries to prevent the possibility of you winning the game twice, and the points will be refunded.
4. Your account is synced after purchasing a Steam game and you have active giveaway entries for that game. The site will automatically remove those active giveaway entries since they're no longer needed, and the points will be refunded.