Conventionally part of the composite letter 13.14 (or “14–15”) in every modern editorial tradition — the Latin Library, Perseus, and Shackleton Bailey all print the material as a single letter under the lower number. The split numbering “13.15” survives in older citation conventions (Tyrrell–Purser and a handful of nineteenth-century commentators), and is preserved here as a citation anchor so that scholarly references to “Ad Att.~13.15” still resolve. The text itself appears in this edition under ../ad-atticum-13-14/Ad Atticum 13.14.