R6700v2 Time Machine/USB Write Access - Mac OS X Mavericks

I have an R6700v2 and a usb drive attached to it, but it won't work with time machine and it seems the reason why is that the router will only provide read-only access to it. There is conflicting information in the manual about this -- page 96 states that the router will only provide read-only access to usb drives formatted in HFS or HFS+, but on page 99 there are instructions for configuring the router and usb drive to work with time machine, which clearly requires write access, and the instructions say to format the drive as mac os extended (i.e. HFS+). Is it possible to configure an R6700v2 and attached usb drive such that they are available for backup via time machine on os x sierra, or even basic write access? Which part of the manual is correct here?