Tiny Humans & Big Booties

I've come to realize that I have no idea how to size knitted things to fit tiny humans. I don't have a tiny human, myself, and I haven't spent much time near one since 2008 when I babysat a newborn regularly. I love them to bits, but I've had limited exposure lately and I have no idea how big their various parts are nor how to compensate for their rapid growth. However, I suspect I need to learn this soon since I'm getting to that age when friends are getting married and starting to think about tiny humans a lot. I made a sweet little Boheme dress for one last January:

Malabrigo Sock, colorway Violeta Africana

I know this dress was greatly appreciated since the baby's mommy sent me photographic evidence that hangs on my refrigerator. I am currently working on some Cutest Booties in anticipation of my advisor's impending little one:

STR Lightweight, colorway Spinel

I love them, I think the pattern is simple and sweet, but I have no idea if they will fit tiny human feet. None of the project photos on Ravelry show them being worn and in my hands, these booties just look big. Way big. As in I can fit four of my fingers inside the cuff, which seems just too big. I'm knitting them at a tighter gauge than the pattern calls for on smaller needles, so it isn't a gauge issue. Perhaps I'm just thrown off because the size says it is intended for newborns and I have no real sense of the size of baby feet beyond 'itty bitty'? I'd love to see these booties on an actual infant. That would be helpful, since I don't have any just lying around on which to test the size of my knitting. Can anybody A) attest to the fit of these booties on a tiny human in real life or B) tell me the approximate dimensions of something they've made that fit a tiny human's foot? That would be terrific!