Thread: What does the Perform Instrument Correction and Apply Total Sensitivity mean?

Dear whom it may concern,
I am using "URL Builder: timeseries v.1",(https://service.iris.edu/irisws/timeseries/docs/1/builder/) to get the seismic timeseries data.

I am struggling in choosing the "Correction" which has None, Perform Instrument Correction , and Apply Total Sensitivity.
I have read the usage of this web but still not clear in the meaning.

What does the Perform Instrument Correction and Apply Total Sensitivity mean?

Can you please give me an explanation or the references?
Thank you in advance,