Outside the range of recorded history, calibration of the 14 clock is not possible.
This means the above calculations are only evolution speculation and NOT backed up by real science.
They have masses of 13 and 14 respectively and are referred to as "carbon-13" and "carbon-14." If two atoms have equal numbers of protons but differing numbers of neutrons, one is said to be an "isotope" of the other.
Carbon-13 and carbon-14 are thus isotopes of carbon-12.
Thus, reports generally specify the ‘raw’ numbers and the ‘fudged’ numbers.
Isotopes participate in the same chemical reactions but often at differing rates.
When isotopes are to be designated specifically, the chemical symbol is expanded to identify the mass (for example, C is not stable.
You probably have seen or read news stories about fascinating ancient artifacts.
At an archaeological dig, a piece of wooden tool is unearthed and the archaeologist finds it to be 5,000 years old.