[talldrinkofwhat]

I think they're talking about box breathing:https://www.healthline.com/health/box-breathing

4s:Full breath in

4s:Hold

4s:Full breath out

4s:Hold*

*this one seems the least natural to me as you're just sitting there, at the bottom of an invisible pool, wasting away.

[baby]

Interestingly Huberman talks about double breath in, then long breath out. https://www.youtube.com/watch?v=rBdhqBGqiMc