The size of the technique was very large because of its high rank, so it would take a few minutes to digest it. He could spare a few minutes so he didn't mind.
But what made things worse was that the Blood Pill Daoist also left her experimental notes and records as part of the Inheritance. This extended the amount of time he needed to use to digest the Inheritance by 100 times.
The experimental notes recorded the process and outcomes of experiments performed over a period of 100 years. So there were thousands upon thousands of experiments and notes. It would take him hours to assimilate everything.
While he was receiving the inheritance, he learned that the Blood Pill Daoist had made the attempt to copy the Inner Pill Art because she was at the peak of the fourth mortal coil and didn't have a way to reach the fifth mortal coil.
