As you are probably aware, e.g. is an abbreviation of the Latin phrase exempli gratia, and means “for the sake of an example”. Technically, it should be followed by an example, i.e., by a single example. In reality, no-one has ever worried about this technicality, and it is not uncommon to find a list of examples following 'e.g.'.
There are many Latin words and phrases used in English, as well as words and phrases from many other foreign languages. When these word and phrases are used in English, it is not uncommon for native speakers to ignore the correct singular and plural distinctions that apply in the original language. E.g.
1/ English uses 'agenda' (singular) and 'agendas' (plural) instead of the Latin 'agendum' (singular) and 'agenda' (plural)
2/ English tends to just use 'graffiti' for singular and plural
instead of the Italian 'graffito' (singular) and 'graffiti' (plural).
A small percentage of English speakers will use these, and other foreign phrases, correctly (i.e., according to their language of origin), but most do not. The longer a foreign term has been adopted into English use, the more likely will its native grammar rules be ignored or forgotten.
As you can see above, I have used 'e.g.' with two examples, which I have numbered to make it obvious that I have done so. I have also seen people label a list of examples using e.g.1, e.g. 2, etc. But I would not recommend this unless it was mandated as the house style of a particular journal.