Explain this scripture (Is 7:14)

[TGBTG]

Ok folks, this is one scripture I can't seem to understand. Maybe some of y'all AFF theologians can chime in.

Is 7
10 Moreover the Lord spake again unto Ahaz, saying,

11 Ask thee a sign of the Lord thy God; ask it either in the depth, or in the height above.

12 But Ahaz said, I will not ask, neither will I tempt the Lord.

13 And he said, Hear ye now, O house of David; Is it a small thing for you to weary men, but will ye weary my God also?

14 Therefore the Lord himself shall give you a sign; Behold, a virgin shall conceive, and bear a son, and shall call his name Immanuel.

15 Butter and honey shall he eat, that he may know to refuse the evil, and choose the good.

16 For before the child shall know to refuse the evil, and choose the good, the land that thou abhorrest shall be forsaken of both her kings.

17 The Lord shall bring upon thee, and upon thy people, and upon thy father's house, days that have not come, from the day that Ephraim departed from Judah; even the king of Assyria.

18 And it shall come to pass in that day, that the Lord shall hiss for the fly that is in the uttermost part of the rivers of Egypt, and for the bee that is in the land of Assyria.

19 And they shall come, and shall rest all of them in the desolate valleys, and in the holes of the rocks, and upon all thorns, and upon all bushes.

So here's the question: The sign that was given to Ahaz through Isaiah from God was that a virgin will give birth. That before that child reached the age of accountability, Damascus and Samaria will lose their kings.

Now, we also know from Matt 1:23 that that prophecy in Is 7:14 is said to have been fulfilled when the virgin Mary gave birth to Jesus Christ.

So was the virgin birth a double fulfillment? As in did a virgin give birth in Isaiah's day (as a sign to Ahaz)?

Or did the virgin birth occur only once (Mary giving birth to Jesus)? If so, how was the sign goven to Ahaz fulfilled?

Or am I just missing it completely??

Thanks AFF scholars!