Late Roman Unit Sizes

[Flavivs Aetivs]

Actually that was my mistake. Synesius was talking about a 240 man unit of Huns. Right below it on Coello's table of sources is Zozimus, who mentions the 4000 men coming from Constantinople to reinforce Rome.

It was Zozimus who mentions it.

Tagmata is a tricky word. Julian uses it to refer to Cavalry in his letter to the Athenians, while using Arithmoi (Numerii) to describe infantry he sent to Constantius.

Zozimus uses it to refer to units of roughly 1200 and units of 666; the first is usually translated as Legions and the latter as Cohorts in English, but there is no distinction.