You would only download a spec if you were going to design your album in a third party program. For example if you wanted to create a design effect that our program did not support, then you would download a spec to use as starting input measurement for creating a canvas in another program.
Our online drag and drop templates work for 90% of people. This is the simplest approach to building an album. Just start a book and drag images into pre-made templates. No third party tools are required and you don't need to click "Download Spec" at all.