'in value over the last six months' vs 'in value in the last six months'

which one is correct:
a)We’ve seen our house diminish greatly/sharply/substantially in value over the last six months.
b)We’ve seen our house diminish greatly/sharply/substantially in value in the last six months.
why we use over or in if one of them is correct?
THANKS IN ADVANCE.

Both are correct; the meanings are the same.

thank you so much sir.