Contentful's publishedVersion Increment logic

Is there documentation anywhere relating to the logic for the amount a content item’s publishedVersion is incremented when published? I’d think it’d be +1 per update, however it seems to be at least 2, and sometimes more (can’t seem to replicate this consistently).

I have a large dataset of video games in a collection tracker, as an example. Querying via GQL for all games (gameCollection) which have a publishedVersion of 1 returns no items, however every query for integers from 2 to 20 (and higher) returns data (2, 3, 4, 5, …). So sometimes it it incrementing by 3, my testing has shown it most often updates by 2, however it seems to never update by 1.

I have a query running on a Lambda which calls out to a third party API and adds or updates items in Contentful, and I want to have that function NOT update an item if the publishedVersion doesn’t match the recorded “lastApiUpdatedVersion” field which takes the publishedVersion and increments by “a number” but knowing what that number is has been inconsistent.

Can anyone shed light on the logic behind the publishedVersion incrementing, and/or suggest an alternative method to know whether the last update to an item was made by an API/function call or a human manually updating in the CMS?