Microsoft Advertising SDK: Windows Phone - number of requests

Question

Sorry for the "bad" title for the problem, wasn't sure how to phrase it. Anyway...

I'm using the Microsoft Advertising SDK (pubCenter) for Windows Phone (no mediation involved). But I'm starting to question if I've done something wrong, yet I'm pretty sure I haven't. It's either:

1. Behaving like it should.
2. The SDK is broken.
3. I'm doing something wrong.

So to determine which one if this is, I'm gonna give you some numbers from my dashboard and hopefully someone can confirm if they have similar numbers or not. See numbers below:

This is for my app on Windows PHONE Store:

Downloads: 28,000 users
Requests: 6,234 requests
Impressions: 5,697 impressions
Fill Rate: 91%
Estimated Revenue: ~$4

In my opinion, the request-count should at LEAST be the same as the amount of downloads. But it's waaaay below. And that MS is calling this "91% Fill Rate" is a joke.

The app on Windows Store (PC & Tablet):

Downloads: 20,000 users
Requests: 228,792 requests
Impressions: 176,108 impressions
Fill Rate: 76%
Estimated Revenue: ~$150

There's an extreme difference in requests between the two platforms. Can someone please enlighten me if this is normal or if something is broken.

Thanks!