Logic and reason leaves no other choice. Since Luke used the words about thirty and not thirty nor exactly thirty, one should assume that Jesus was not thirty when he began his ministry. If he was 29 or 31, thats a three year swing completely plausible and logical. If he was 28 or 32, thats a five year swing again, completely plausible and logical.
The seven year swing comes from my use of 27 and 33 to be considered about thirty.
So how do your calculations work if you use an age other than exactly 30? About doesnt mean exactly.
Just curious.
When Moses wrote "Torah" he said thirty was the age a young Israelite should begin his priestly duties.....so I believe that Jesus also began his about the same time. I think we should accept the scripture for what it says....nothing more, nothing less. Luke did not say He was about 29.