By what factor does the $3'$ to $5'$ exonuclease proofreading step typically improve fidelity over the initial insertion rate?

Answer

About 100 to 1,000-fold

Proofreading brings the error rate down by a factor of about 100 to 1,000-fold compared to the initial incorporation error rate.

By what factor does the $3'$ to $5'$ exonuclease proofreading step typically improve fidelity over the initial insertion rate?
DNAaccuracyreplicationProofreading