To the best of my knowledge, last time I check, SlideMe uses a counter.
If only 1 person using 1 account, downloads across his/her 3 devices it will count as 3 downloads. If he/she updates or re-download, that too will count as another download.
Whereas Google Play only count per account, even if that person download using 10 devices, update and re-download multiple times, its still count as 1 if he/she uses the same account.