What does citing “blood the amount of a dirham” directly establish in this passage?

Narrator Criticism, Integrity and Precision: Standards of Scholarly Appraisal

• Identification of a report associated with Rūḥ b. Ghuṭayf and criticism of his transmission
• The phrase itself explicitly establishes Rūḥ’s precision and trustworthiness
• Its purpose is to establish a juristic consensus about a fixed quantity of blood
• Ibn al-Mubārak conclusively accepted the report as an authentic Prophetic narration