I'm definitely not an expert in this area, but keep in mind:
1) Users may start your app downloading then move on to other things and forget about it. I know I've done this with apps numerous times.
2) They may see they have to download the free folio, start the download, navigate away from the app, and then forget about it. I believe this is what Johannes means when he says it's the "biggest problem" with multi-folio apps.
3) We'll only report a folio download once the full folio has been downloaded. It's possible that your users are starting the folio download, viewing the folio as soon as enough has come down to open it (but not the full folio), then leaving the app. If they don't continue the download that partial download won't be reflected in your totals.
Neil
