Manuscript variant · documented
What the source reads — the Hebrew numbering — 150 psalms, the '23rd psalm' is Psalm 23
What this version reads — the Greek/Latin numbering — Psalms 9-10 and 114-115 merged, 116 and 147 split, so most psalms run one number behind (Hebrew Ps 23 = Vulgate Ps 22)
Not a change of text but of counting. The Septuagint and Vulgate divide the Psalter differently from the Hebrew, so through most of the book a Vulgate reference sits one number behind the Hebrew/English — the reason 'Psalm 22, they pierced my hands' is Psalm 21 in the Latin.
Manuscript variant · documented
What the source reads — the Vulgate counts the Hebrew superscription ('A psalm of David…') as verse 1
What this version reads — Martini folds the title into verse 1, so his verse numbers run one behind the Vulgate through much of the Psalter
Not missing text — a numbering convention of Martini's edition. Where the Vulgate gives the psalm's heading its own verse number, Martini absorbs it into the first line, shifting the count. Verified during ingestion.