What is relevant to generality is not that as a matter of fact the information is true of many things, but the fact that a thinker can make sense of it being true of many things (or of different things in different possible situations). Conversely, what is relevant to singularity is not the fact that the information in one’s file is true of just one thing, but that one cannot make sense of it as being true of many things.Scotus says
Terminus communis secundum quod habet rationem communis est natura prout concipitur sub ratione ‘dicibilis de pluribus’, et ita suppositum est natura concepta apud intellectum sub ratione ‘indicibilis de pluribus.* “A common term, according as it has the nature of the common, is a nature as conceived under the aspect ‘predicable of many,’ and so a suppositum is a nature conceived in the understanding under the aspect ‘incapable of being predicated of many".A suppositum is a technical term difficult to translate, and is often left untranslated. Scotus here often uses it to mean any object that falls within the range of a common term (or the 'value' of a variable, if you like). Thus any man is the suppositum of the common term 'man'.
* Book I Question 6 n43. As some readers of this blog will know, I am working with Jack Zupko on an English translation of this early work of Scotus. This may even get published this year, who knows.