I apologize, but I don't have specific information about where in the Torah Anthology book it talks about Shevet Ephraim leaving Egypt early. The Torah Anthology is a multi-volume work, and without access to its full contents, I cannot pinpoint the exact location of this particular topic.

However, I can provide some general information about the story of Shevet Ephraim's premature exodus from Egypt based on other Jewish sources:

The midrashic tradition tells that some members of the tribe of Ephraim miscalculated the end of the 400 years of exile prophesied to Abraham and left Egypt 30 years too early12. This resulted in a tragic outcome, as they were attacked and killed by the men of Gath when they tried to enter Canaan1.

This event is often connected to the verse in Psalms 78:9, which states: "The Ephraimites, armed with the bow, turned back on the day of battle"1. According to the midrash, this refers to the Ephraimites who left Egypt prematurely and were defeated.

The story is seen as a cautionary tale about the dangers of trying to force the end of exile before its divinely appointed time5. It's also sometimes interpreted as foreshadowing the role of Ephraim (specifically Moshiach ben Yosef) in the future redemption7.

While this story isn't explicitly mentioned in the Torah itself, it's a well-known midrashic tradition that is often discussed in commentaries on Exodus and in discussions about the calculation of the years of Egyptian exile.