”for 15 years” vs ”for over 15 years”

”for 15 years”= Exactly 15 years. 剛好 15 年, 整整 15 年.
”for over 15 years”= More than 15 years. 超過(多過) 15 年.
John & Mary married for 15 years.
John & Mary married for over 15 years.

1.
已超過 15 年
The number of people unemployed increased at the highest monthly rate for over 15 years.

2.
接近15 年或剛達 15年．
The number of people unemployed increased at the highest monthly rate for 15 years

For examples.

I have been in Hong Kong for 1 year. 即我已來到香港將近１年．
I have been in Hong Kong for over 1 year.即我已來到香港將超過１年．

意思相似，但不同．

"The number of people unemployed increased at the highest monthly rate for over 15 years" the point is " over 15years ",not exactly 15 years but more than 15 years


and

"The number of people unemployed increased at the highest monthly rate for 15 years" It means exactly 15 years, when they say it should be 15th years since the number of people unemployed started to increase.