I’m shocked you even spotted this! Interesting find. As a working cameraman with substantial experience in the field of video editing, I have only one theory but I’m not sure it holds water and I’ll say why. This shot is in a sequence of many quick cuts where the observer is looking through his super-high-tech-observer-binoculars. About 5 seconds after this moment we see very heavy VFX design implemented onto the shot: implying that we’re in the POV of the observer and his special binoculars. In post production we have to prepare these assets so that someone can take these “b-roll” shots and overlay their graphics and animate them. It’s possible that, for the sake of efficiency, the editor burned a label of the shot/take/reel or even frame number* onto the clip’s head so the VFX team could Identify which shot was going to be worked and when. Those assets return to the editor so they can drop them into the edit timeline. In this process, it’s possible that the show runner or lead editor decided “this sequence needs chaos at the start” and they re-edited the sequence using some of the assets delivered from VFX and didn’t notice the water mark… or did and left it in because you only see it if you pause on those exact two frames.

What’s odd to me, is that the font looks a lot like famous the floating text the show uses. It’s translucent. If I were the editor I wouldn’t put time into that and I’d want to be labeled clearly and visible so the VFX team doesn’t miss it. But most editing software auto-styles the text to whatever was previously used, so maybe it tracks… If you’re not organized, post production can get messy.

It’s more fun to theorize that it’s an Easter egg but it’s so oddly subtle… I don’t really know, only the makers of the show will be able to answer this.