Does Numbers 3:43 refer to "all" the firstborn sons of Israel?

Question

Total number of firstborn sons

(KJV) Numbers 3:43

43 And all the firstborn males by the number of names, from a month old and upward, of those that were numbered of them, were twenty and two thousand two hundred and threescore and thirteen.

Total number of males above twenty in the census

(KJV) Numbers 1:46

46 Even all they that were numbered were six hundred thousand and three thousand and five hundred and fifty

Could the over six hundred thousand males have produced only the figure mentioned above?

Does the figure of fisrtborn sons mentioned in the above text refer to all the firstborn sons of Israel or only to those that were born after they left Egypt?

Answer 1

Referrence
Exodus 12:2,41
Exodus 16:1
Exodus 19:1
Exodus 40:17
Numbers 1:1Date
15^th day, 1^st month
15^th day, 2^nd month
3^rd month, 1^st year
1^st month, 2^nd year
2^nd month, 2^nd yearEvent
Israel left Egypt as dawn broke
Israel came to the edge of the wilderness of Sinai
Israel entered the wilderness of Sinai
The construction of the Tabernacle began
The Tabernacle was completed, and Israel was numbered

The nation was only 14 months into its journey when Moses numbered the people. Since the number of firstborn sons is given as 22,273, then it would also represent the number of new fathers, i.e. ~4% of the male population 20+ years old. So, in all probability these are the firstborn sons delivered during the 14 month journey thus far.

The crude birth rate represented by the population numbers given here, is approximately 37 per 1000 during the 14 months, but when adjusted for 12 months, it is around 32 per 1000. This birth rate reflects what is said about the Hebrews early in Exodus:

⁷And the children of Israel were fruitful, and increased abundantly, and multiplied, and waxed exceeding mighty; and the land was filled with them.
...
¹⁹And the midwives said unto Pharaoh, Because the Hebrew women are not as the Egyptian women; for they are lively, and are delivered ere the midwives come in unto them.
-- Exodus 1:7,19 KJV

By way of comparison, that's 2.5 times the birth rate in Australia in 2015. Here's a link to crude birth rates (per 1000) around the world in 2015. Australia's rate in 1960 was 22 per 1000, so it has almost halved within the last two generations.

Conclusion

The 22,273 firstborn sons are those that were born after Israel left Egypt. The nation was born as the 14^th day of Abib became the 15^th at the beginning of the 1^st year of its existence, and these 22,273 sons were the firstborn of the new nation.