Two different statistics.
Kobo has 47% of the sales life to date (and 55% over the last year) in dedicated e-ink e-readers. That's a study strictly looking at e-ink device sales.
This new study is looking at e-book sales, not e-reader sales, so blends in people who read on tablets, laptops, smartphones, etc. Given all the devices and all the e-book stores available, Kobo having 27% of that fractured market is actually a huge accomplishment, especially since Kindle, Sony, iBooks, etc., have captured less.