Unless it seems immediately relevant to the Carnival's purposes, Lambert's going to shrug and ... tuck the binder under his arm for future perusal. Why bust his head trying to memorize information when he can straight up steal it and pore over it later?

"Why get complicated if you've got something that works?" The skeleton's words get him a smirk and a shrug. If the shoe fits ... "Other dimensions, huh? sounds a lot more like what we've got back home. There aren't any post-Conjunction creatures--" The air quotes around the term are implied, if not actually acted out. "--that could do what you're describing, though."

And he waves a hand at the other shit in the room, since none of it seems to surprise Sans very much. "You know how to use these? Think we can find anything else out?" Answers the question about how much he knows, anyway.