Difference of to be exact and to be specific

Question

Are there any differences between to be exact and to be specific?

For example,

It took decades for them to finish their mind-blowing invention, 24 years to be exact.

and

It took decades for them to finish their mind-blowing invention, 24 years to be specific.

Can we use them at the start of a sentence and is to be exact used to literally indicate exact things? While to be specific is explicit about a thing? What are your thoughts?

Answer 1

To be exact implies that it took exactly 24 years (so, not a round number of decades).

To be specific means that 24 years was the particular period of time that it took.

So, in effect, both mean the same thing in this context, with a slight difference in emphasis.