What did God designate Jacob to be in relation to the firstborn?
God designated Jacob to be the firstborn, so he was to take the role and position of the firstborn. According to God's own reckoning, Jacob was not lying when he claimed that place, because God had assigned him that exact standing and future position.
Les explains that when Jacob said to Isaac, “I am Esau thy firstborn,” it can seem like a bold-faced lie. But the context must be viewed in light of what God Himself had designated: Jacob was to be the role of the firstborn. Therefore Jacob was not lying; he was in his position now, the firstborn. According to the way God reckons things, this is exactly where Jacob was going to be. He was going to be the role of the firstborn. Les also asks whether God was unfair, and answers no, because of what God had seen in the makeup of Esau.