People wonder how millions of years could be squeezed into the biblical account of history. Christians, by definition, take the statements of Jesus Christ seriously.
So, we have a “clock” which starts ticking the moment something dies.
This will make old things look older than they really are.
Also, the Genesis flood would have greatly upset the carbon balance.
Anything over about 50,000 years old, should theoretically have no detectable C.
That is, they take up less than would be expected and so they test older than they really are.The flood buried a huge amount of carbon, which became coal, oil, etc., lowering the total C ratio in plants/animals/the atmosphere before the flood had to be lower than what it is now.