Between the 4th and 12th centuries, seven or more correctors worked on this codex, making it one of the most corrected manuscripts in existence. Tischendorf during his investigation in Petersburg enumerated 14,800 corrections only in the portion which was held in Petersburg (2/3 of the codex). According to David C. Parker the full codex has about 23,000 corrections. In addition to these corrections some letters were marked by dots as doubtful (e.g. ṪḢ). Corrections represent the Byzantine text-type, just like corrections in codices: Bodmer II, Regius (L), Ephraemi (C), and Sangallensis (Δ). They were discovered by Edward Ardron Hutton.