There's a detailed graph of it here:
What is the most precise reference for your query is the Time-Frequency graphs in black and green, also called waterfall graphs, spectrographs, sonograms and so forth.
On the Y axis, the width of the green smudge is about 30-50Hz, That's the frequency-uncertainty for the TF graph for every wave of the roughly 10 waves that make up the signal.
That's the actual real measurement that LIGO returned, and there are idealized versions here with an uncertainty range of about 5Hz.
If you are interested in sound theory, you can research about Wigner-Ville TF graph, which is the most precise sound analysis mathematics known, and which uses quantum uncertainty estimates to minimize the quantum uncertainty of placing single audio waves in time at a given known frequency. If you have java JVM you can compute a more deeply processed TF graph using sonogram 4 visible speech demo version.
As an synth-reverse-engineering sound scientist, I have to say that the precision of the wave is incredibly clear, it's the same as recording an individual bird chirp from 20 meters away on a clear microphone. Gravity actually has sound, like a bird call, except it's not carried by air compression it's carried by space time at c.