This came up in the following thread: Question about pet slots!

It would seem that the pet slot that was recently given out at the Quest-a-thon was categorized as a "new slot addition" instead in the "awards and prizes" section. As evidenced by the users who said they've never bought or otherwise gotten a pet slot, and my stats, which say 56/55.

This matters because once you hit that 55 limit, you can't go any further, and I'm sure there are some people out there who would rather have this prize categorized as a prize so that they have space to buy more slots as they're nearing their limit.

It looks good to me!