The measurement isn't always on the bone fragments themselves.
To arrive at their date of 32,500 years ago the C14 reading in the Neanderthal bones would have been c 2% of original ratio, achieved by a C14 clock count reading of c 6 counts per second.
If we now rework this date using the short 10,000 year period of C14 build up and the 2% of original ratio ( 6, counts per second ) used in the evolutionists original calculation.
Whether it's currently on an upslope or a downslope, either way, extrapolating that slope back into the past in an unchanging way is just lying; if it's up now, it's been down before more than once, and if it's down now, it's been up before more than once.
Carbon dating originally could only give ranges with a much larger degree of uncertainty than is used today, because it was not known precisely how much higher or lower the atmosphere's ratio had been in the past (although fluctuation including both increases and decreases was already known to be possible).
It now seems feasible to reliably date bones up to 55,000 years.
New developments in laser ablation mass spectrometry permit the in situ analysis of U-series isotopes, thus providing a rapid and virtually non-destructive dating method back to about 300,000 this (
But measurements of the C-ratios in the wood from separate rings from the same trees solved that.
Each tree ring can be pinpointed to a precise year when it formed, because the record is continuous to the present, so each ring's actual ratio could be compared to the ratio you'd predict it to have if the atmosphere's ratio had been constant (in other words, if the wood had originally been deposited with the same C-ratio as wood today would be deposited with).
When we calculate back the equation to zero point of C14 in the atmosphere using this increasing 25-38% present 'greater build up of decay ratio' in the atmosphere we find we get a starting date for the C14 build up process in the atmosphere by cosmic ray bombardment of only c10,000 years ago.