At the same time, the critical text should document variant readings, so the relation of extant witnesses to the reconstructed original is apparent to a reader of the critical edition. In establishing the critical text, the textual critic considers both "external" evidence (the age, provenance, and affiliation of each witness) and "internal" or "physical" considerations (what the author and scribes, or printers, were likely to have done).
Why is it important to document variations in witness texts when compiling a critical text?
so the relation of extant witnesses to the reconstructed original is apparent to a reader of the critical edition.