KOBO SALES RANK MYSTERY ISSUE ???

My E-book *Crossroads and/or Illusions - Coping with Plug & Play Ideology * (ISBN* *978918775134) has been among top 3 % of titles for almost  six months at Kobo Retail portal. 

Kobo Sales Rank on November 14, 2014

• #1871 in Nonfiction > Social & Cultural Studies > Social Science this category has 74439 books
• #835 in Business & Finance > Economics this category has 29290 books
• #1284 in Nonfiction > Social & Cultural Studies > Political Science this category has 51656 books.

Kobo is not giant as Amazon but belongs to major retailers, therefore it doesn't sound logic that there is no sales at all with such sales ranking.

Kobo doesn't want to disclose sales data for e-book is published through Publisher;on other side my Publisher says that there is no sales at all and that Kobo Sales Rank is more "Mathematical Algorithm" than figure that shows exact book sales. 

I ask authors what are their impressions about "Sales Rank", in particular, with Kobo e-book retailer.

Whom Am I supposed to believe - Publisher, Me, Book Retailer or.....???

Please, help me If you know How Kobo Sales Rank works.

Confused Author

Aleksandar Krzavac

E-mail aleksandarkrzavac@gmail.com