Commentators overwhelmingly agree that Stephen's use of "four hundred years" is a round number from Genesis 15:13. Other passages, like Exodus 12:40, use 430 years. Scholars explain the longer figure likely includes the time the patriarchs sojourned in Canaan before Egypt. The main point is that Stephen's focus was not on precise chronology but on the theological truth of God's faithfulness through a long, prophesied trial.