How many years were the children of Israel in slavery in Egypt?

How many years were the children of Israel in bondage in Egypt?

Genesis 15:13 and Acts 7:6 indicate that the Israelites  would be afflicted 400 years. Exodus  12:40 states the sojourning of the children of Israel in Egypt was 430 years; Galatians 3:17 states that from the giving of the promise to Abraham to the giving of the law by Moses was 430 years. How can the above Scriptures be reconciled to one another? What does Genesis 15:16 mean?

There is no real discrepancy, but we must note what is said in each case, and take into consideration the universal permission of an occasional use of round numbers. The difficulty of Genesis  15:13 arises from limiting the “four hundred years” to the AFFLICTIONS in Egypt, whereas the expression governs the whole verse, and I feel sure that the earlier expression, “thy seed shall be a stranger in a land that is not theirs,” would go further back even than Egypt, to what characterised the lives of Isaac and Jacob and his sons, even before they went down there. That this number—400 years—then is to be taken in this general and round number way, seems clear from Galatians 3:17, which dates the 430 years exactly from the promise to Abraham (Gen. xv.) to the giving of the law in the third month of the Exodus (see Exodus 19:1). This tallies with the 430 years of Exodus 12:41, a verse generally read as though it affirmed that the children of Israel sojourned that period in Egypt, whereas it says that the sojourning (i.e., I take it as including the whole period of their sojournings either in Canaan or Egypt) of the children of Israel (who dwelt in Egypt) was 430 years. That is, they were always characteristically “sojourners.” This is shown, I believe, to be the case in Genesis 15:16, where the Exodus is specified as to occur not 400 years after their arrival, but “IN THE FOURTH GENERATION.” This harmonises with the genealogies of Exodus 6: , where we learn that Kohath was a son of Levi, and that Amram, the father of Moses and Aaron, was the son of Kohath, i.e., four generations. Notice the ages of Levi (v. 16), of Kohath (v. 18), of Amram (v. 20), which specify this.