The circle with crossbar is a stemless phi rather than a theta, in my view, and the letter before phi, is either a lambda or a mu: what might look like a crossbar of alpha is likely an accidental stroke, slip of a writing implement. Below that letter is another slip of the writing tool: the slips, in my view, are indicated by thinner lines than intentional strokes. Graffiti on the interior of a cup are usually either sympotic or dedications, less typically - ownership. It is possible to restore a name here, e. g. [Νυ]μ̣φο[δορος], in the Nominative or in the Genitive. Alternatively, [- -]Λ̣ΦΟ[- -] could be read [Δε]λ̣φό[ς] in the Nominative or in the Genitive - this name is attested in Chersonesos in the IV and III cent B.C.E. (V4-17004, V4-16997, V4-16998), but in Olbia-Borysthenes only in the II cent C.E.