There are two primary reasons why your sales report may be showing fewer copies sold than expected.
Most commonly, the "missing" sales are due to the 1-3 week delay that sometimes occurs between the date the book is sold through an online retailer and when the distributor prints and ships the order, the latter being the date that the royalties are actually marked as earned with the distributor. If, for example, a book is purchased through a retailer like Amazon on June 20, this sale may not be printed and shipped until early July, and therefore will not be reported until the July sales report is released.
The second possible reason for this takes place when retailers are fulfilling orders from their inventory which has been built up during a previous month. When a book is showing some consistent sales, retailers are more inclined to stock up on books in anticipation of continued demand. This is usually triggered by a book selling many copies over a short period of time, and allows the retailer to fulfill faster shipping.
Therefore if a retailer like Amazon stocks up on 20 copies of your book in February, but doesn't sell all of them until May, all 20 sales will be reflected in the February report and not the May report, regardless of the month in which the reader actually purchases the book; recall that royalties are marked as earned when the distributor prints the book, not when the book is purchased through the retailer.
Unfortunately, the reports we receive only specify when the books were purchased from the distributor, and we are not able to distinguish between sales from customers vs retailers, nor can we tell through which specific retailers books have been purchased.
We take the accuracy of our sales reporting extremely seriously, and our reporting process is automated, accurate, and removes nearly all chance of human error -- with both automated and human quality checking steps along the way.
With that said, if you have a specific question or concern with any royalty report, we will be happy to verify the accuracy of the report released through Octavo by cross-referencing with the original distributor reports, just send us an email at firstname.lastname@example.org.