Excellent question and thank you for asking it. In this forum, under the heading of "DANIEL" I did a verse by verse comprehensive Bible study about 2-3 years ago. I would encourage you to search it out and go through it as I detailed in there the answer.
However....It is NOT math but actual interpretation of what is said.
Stongs #7620 says that the Hebrew word for "WEEK" is literally translated a "a time peroid of seven".
So then, Upon seeing this word one must ask, "a time period of seven whats?"
Daniel chapter 9 uses the Hebrew word (שבעים ~ Shavuim) to represent a period of time multiplied by seven. For various reasons this word is translated as “weeks” and means a multiple of seven years rather than a multiple of seven days.
So then, by that understanding, lets read Daniel 9:1 to see what the word "WKKS" means bu context as used in the Scriptures...........
" In the first year of Darius the son of Ahasuerus, by descent a Mede, who was made king over the realm of the Chaldeans the first year of his reign, I, Daniel, perceived in the books the number of YEARS that, according to the word of the Lord to Jeremiah the prophet, must pass before the end of the desolations of Jerusalem, namely, seventy years."
So Daniel was using the word "Shavuim" to mean a "SET OF SEVENTY YEARS". That means 70 x 70 or 490 YEARS.
From the study in Daniel I posted we see this............
"In verse 24, Gabriel says, “Seventy ‘sevens’ are decreed for your people and your holy city.” All commentators and those I have read and accept, agree that the seventy “sevens” should be understood as seventy “weeks” of years, in other words, a period of 490 years just as Daniel said. These verses provide a sort of “clock” that gives an idea of when the Messiah would come and some of the events that would accompany His appearance but does not in any way set a date.
The prophecy goes on to divide the 490 years into three smaller units:
1. one of 49 years,
2. one of 434 years,
3. and one 7 years.
The final “week” of 7 years is further divided in half. Verse 25 says, “From the time the word goes out to restore and rebuild Jerusalem until the Anointed One, the ruler, comes, there will be seven ‘sevens,’ and sixty-two ‘sevens.’” Seven “sevens” is 49 years, and sixty-two “sevens” is another 434 years:
49 years + 434 years = 483 years.
Those final Seven years are what has not yet been lived and is called The Tribulation Period. They begin when the church is removed and end when Jesus returns 7 years later.
