Emperor Justin II was a consul in 566 and 567, so the third year mentioned by Donatus will be 569 or 570.
The same Donatus as a deacon in 561 wrote a gloss in another codex he owned which contained Rufinus's De adulteratione librorum Origenis and his Latin translation of Origen's Peri archon, it was later copied in the tenth century to ms. Metz 225 (printed by Koetschau in the introduction to his edition of Peri archon, 1913: lx). See also Hammond Bammel 1984: 367.
After the demise of the Roman administration in the province of Noricum, the body of saint Severinus was translated from Lauriacum to Castellus Lucullanus near Naples where the noble woman named Barbaria founded the mausoleum for the burial (see Eugippius, Life of Severinus 46, [XXXXXXX]). Later Eugippius founded a monastery there and most probably in its library Donatus read and commented on Ambrosiaster and Origen. See also Hammond Bammel 1978: 442, 445.