This means that even though God sees the entire string already played out by individual choice within the string, which individuals could not see the entirety and thus made choices as in freewill. The choices within the string of events foredestined their salvation. But God sees the end result, so knows how it would play out and thus says "I foreknew".
But, then, who here has discussed this over a beer with the Lord of Hosts?
The All-Father wove the skein of your life a long time ago. Go and hide in a hole if you wish, but you won't live one instant longer. Your fate is fixed; Fear profits a man nothing.