What does a day at the rate of ten books mean?

Standard. "Rate" in "ten books a day" is the standard meaning here. The literal meaning of "ten books a day" is based on writing ten books a day. This sentence was written by Wen Zhiming, a calligrapher in the Ming Dynasty. When writing money, take ten books a day as the standard, and your calligraphy level has improved rapidly. Solemnly declare: The above answers are for reference only.