As a basic policy, we'll release all the chapters from the new issues that come out, including sequels. Before we work on any other backlog content from a certain magazine, we'll try to pick out the previous parts to a story and release those. If it's just a single prequel chapter from a recent issue, we might make an exceptions and do that right away. The data for older content can be unreliable (either the format changed over the years, or we simply don't have it yet), so picking out selected chapters from the backlog might not always be an option right now.
If you don't want to read them out of order, I suggest ignoring the chapters for now and wait until the first part is released later on.