Late Roman Unit Sizes

[ValentinianVictrix]

Is there evidence to disprove the arithmoi/numeri could be another term for vexillation?
Ammianus (31 11 2) has Valens send a number of numeri each of 300 men from each legion to meet the Goths at Adrianople. The inscription of Hadrian’s address to the legionary base at Lambaesis mentions that five men from each century were sent to the third legion (III Cyrenaica). Could this also apply to what Ammianus is describing?

Steven, where do you get the information that Valens sent 'numeri'? Not from Ammianus' work because this is what he wrote-

'Unde cum itinere edicto per tesseram Nicen venisset, quae statio ita cognominatur: relatione speculatorum didicit refertos opima barbaros praeda a Rhodopeis tractibus prope Hadrianopolim revertisse: qui motu imperatoris cum abundanti milite cognito, popularibus iungere festinant, circa Beroeam et Nicopolim agentibus praesidiis fixis: atque ilico ut oblatae occasionis maturitas postulabat, cum trecentenis militibus per singulos numeros lectis Sebastianus properare dispositus est, conducens rebus publicis aliquid, ut promittebat, acturus.'
'Having commanded a march from there by written order, he came to the military post called Nice, where he learned from the report of scouts that the barbarians, laden with rich spoils, had returned from the lands at the foot of Rhodope to the neighbourhood of Hadrianopolis; they, on hearing that the emperor was on the march with a large force, were hastening to join their countrymen, who were staying in a permanent garrison near Beroea and Nicopolis. At once, as timeliness of the offered opportunity demanded, Sebastianus had been directed to choose three hundred soldiers from each legion and hasten to the spot, to do, as he promised, something advantageous to the state.' Amm BkXXXI, 11.2