Joe Biden: "I don't know what I'm signing" before signing executive order

Simon Parkes mentioned something that made me look up and find this video. Okay, I'm sorry it's VERY hard to hear, BUT, if you listen a few times with the sound up it sounds a bit like Biden’s saying, “I don’t know what I’m signing huh?” and then Kamala says something like “sign it anyway”. Then after looking at one of the things he just signed gives Kamala a funny look and says, pushing the signed EO over, “Take this to the President”. Whatever he exactly says, he’s certainly mumbling about something not very confident about what’s going on. And why does his assistant need to duck into the picture to move the other books out of the way. Is that so he doesn’t confuse them and try to sign them a second time?
Someone on one of the comments mentioned that if you sign legal documents but are mentally incapable it invalidates them, or something to that effect. Interesting.
PS. I just looked on YouTube to compare Trump and Obama (ugh!) signing their Executive Orders. They looked significantly more with it mentally and physically. Not hard.