The history of alpha.
https://comicbook.com/tv-shows/amp/news/tales-of-the-walking-dead-dee-alpha-timeline-explained-when-does-dee-take-place/
I made it a point to record this series and I am now getting into it. I just finished this episode that you are referring to and liked it very much.
This anthology series is a refreshing break from the TWD show and of the episodes I have seen, each one stands alone and has been very well done. I think I have 2-3 more to watch to complete the series.
A couple of them are not very well scripted, directed and produced but the Alpha segment was the best by far.
The one I watched last nite, I believe it was the one after the Alpha episode, about the oriental girl and the bearded guy who was doing experiments and tests on a particular walker who was his buddy before getting bitten. I also found this episode tedious and not that good.