Walter Burley's Treatise on Obligations (1302) is also suggestive:
‘Positio, as the term is used here, is a prefix to something statable [indicating that the statable thing] should be held to be true. ... If it covers a composite statable, either it is a composite formed by means of a copulative conjunction – in which case it is called conjoined positio – or it is formed by means of a disjunctive proposition and is called indeterminate positio.’
Thus Kretzmann/Stump's Cambridge Translations I, p. 378.