If you think there's a chance of it not being used in the 2 hours, it's very safe to leave it at rt for the 4h and then store it, but it's of course always ideal to put it into whichever storage temperature is the most stringent for the time it's going to be stored. (For example, breast milk that will eventually go into the freezer for several months is better to be put there immediately rather than left in the refrigerator for several days and then put in the freezer. It's nitpicky really, and you can't always have that level of foresight, but if you ever end up with excess milk and decide to donate or you end up needing to use freezer milk that's on it's last month of safe storage in the deep freezer, it gives a lot of peace of mind to know that the milk was handled with stringent food safety standards in mind.)