Why did Michonne and Daryl have giant X's on their backs?

[stpauliegirl]

They both were located in the lower left area of their back and appeared to be a scar or a brand.  We were shown them in separate scenes where they were getting dressed (Michonne) or changing his shirt (Darly).

[Money Honey]

I looked it up, and it said that maybe the two were captured.  Michonne was quick to recognize
Magna's prison tattoo. Angela king will reveal them at some point in the future.  They are in the
same spot, and identical.  It happened after Rick left, and with six years passing, there are
things that could have happened.

Rick wasn't the only one to leave in "What Comes After".   It was Maggie's last episode also.  She
had scheduling conflicts with her new show.  Angela King explained to the Hollywood
reporter that's the last of her for this season.  She may, or may not be back.  That is all I found.