Very false!
The Bible does give an exact number of years from Adam to Christ, through the geneologies, and we know the number of years from the birth of Christ (Sept 29, 2BC by our calendar) and the fact that God made it a point to tell us is proof enough that it is important.
No. Some people THINK there's an exact number of years, but there ain't. Like I said, the various translations--Septuagint, Peshitta, Masoretic text--give different numbers for those geneologies, and they may not even be exhaustive. When you open up your King James or whatever, the translator made a decision which ancient authority to follow. That decision may or may not be correct--but it sure ain't infallible.
And we do not know with certainty the date of Christ's birth either.