I completed a 10 Dawnbreaker last night (we didn't time it, but it was completed) but KM is currently still showing I have completed a +9.

I uploaded a log from last night to make sure we did complete it.
https://www.warcraftlogs.com/reports/gTb3F6V7KtzZrNCQ#fight=last

I updated the raider.io app about an hour ago to see if maybe that would help.

Here's a screenshot of KM in the game currently.

This is being fixed in the release today (1.3.7). Sorry for the delay!