This may happen depending on point of access that a user chose to search a database. Here's a typical scenario:

• A publication may be available in 2 or more different ProQuest databases.
• A user didn't perform a cross search across ProQuest databases but instead, chose a specific database (A), performed a search then retrieved an article.
• Another user or the same user chose a different database (B), performed a search and retrieved an article that belongs to the same publication as in database (A). 
• In this case, the same publication will show up under both databases (A) and (B).
• Depending on the articles retrieved, the retrieval numbers could be different for each database.
• There's no double counting or usage inflation in this case.