Sans is becoming reluctant again, at that question. He runs his hand over his skull, scratching the surface with his claws slightly as he tries to figure out how to quantify it.

"Eh... hard to say..."

The truth is that Papyrus had been forgetting things for a while before that already - or one particular thing anyway - but there was nothing to be done about that. Maybe it wasn't relevant? He's not sure, but he doesn't want to talk about it right now.

"I didn't always remember everything myself, just... bits and pieces. Enough to understand." His expression flinches, for just a moment, with something like the memory of pain. "But... when I found the carnival, I asked to know more as part of my contract. It worked but... it's a lot."