Eh, probably nothing to worry about.
This isn't the first time multiple sixes have appeared. Feel free to also check Gaster's datamined stats (spoilers) if you still don't know why.
Edit - Check out Phoenix Prime's dub!
And Jamadub's! (Spanish)
And Solros's! (French)
And Puzzle Channel's! (Russian)
Português do Brasil
Alphys, Asgore, Mettaton, Sans, Papyrus (c) Undertale: always drink plenty of malk
OOOOOOOOOOOH. This LITERALLY JUST HIT ME IN THE FACE. Ok, I know I might sound stupid for just now catching onto this, but bare with me. Ok, so I think anytime someone falls into the core, they’re forgotten about, which is why no one could report a missing person; their buddy wouldve immediately forgotten about them, as would have anyone else who knew them. They wouldve just ceased to exist, almost like they were never there. So I think that when Gaster got erased, Sans and Papyrus forgot all their memories because Gaster was the only thing they ever knew, the only person they ever knew. He practically gave them all the things they ever had in their minds. So... yeah. Sorry again for all that everyone, just had to type it out. 😅