Pinout for the header on the Onyx BOOX Leaf

I've recently obtained an Onyx BOOX Leaf, a nice e-ink android tablet. One of its features is that it supports magnetically attached cases with physical buttons for page turning. This is done through three pogo style pins on the left side of the device, with each pin being about 1mm wide, with the pins all spaced about 3mm apart.

These are connected exactly how you'd imagine - shorting the middle pin to the top or bottom will actuate the button. However, weirdly enough, the official (and as far as I can tell, the only available) case connects these buttons backwards - the lower button (by default, page forwards) shorts the middle and upper, while the upper button (page backwards) shorts the middle and lower. I have no idea why this is the case.