To directly answer - here is a quote from the SAP Crystal Reports:
Applicants were asked to list the number of abstracts, presentations and publications they reported in their ERAS applications. This information is self-reported and may include peer-reviewed articles, abstracts, poster sessions, and invited national or regional presentations. Some residency programs may independently verify and even review publications for applicants in whom they have an interest, but most probably do not. Many applicants report abstracts, presentations, or publications, sometimes dozens or even hundreds. In the individual specialty sections, we distinguish between no publications, 1 to 5 publications, and more than 5 publications. Chart 9 shows the average number of publications by applicant type, preferred specialty, and Match outcome. U.S. seniors averaged 4.2 publications with 77.3 percent reporting at least one publication. Independent applicants reported, on average, slightly fewer publications (3.9); however, a smaller percentage (61.8%) listed any publications. For competitive specialties such as Dermatology, Neurological Surgery, Orthopaedic Surgery, Otolaryngology, and Plastic Surgery, independent applicants reported considerably more publications than U.S. seniors, but the same was not true for less competitive specialties like Family Medicine and Pediatrics
This makes no distinction between WHEN or WHERE these abstracts, presentations, or publications were made. You can count any of these events from your life if you wanted to, not sure anyone would care though.
How can someone have 5-15 of these? It seems very easy to do. You can pump out abstracts/posters, and presentations very easily as those above have said. Publications are moderately difficult, depending on your field, team you work with, and patience/planning.
Edit: Notice the line above that says "Many applicants report abstracts, presentations, or publications, sometimes dozens or even hundreds." Non-trads definitely would bring the average up if they were PhD or other academic type before medicine.