The Category/Document count is at the top of the Checklist and shows you:
How many 'categories' have been generated for your checklist. A Category might be PAYG Employment vs Self-Employed
How many documents have been generated for your checklist. This will be the total number of documents, within the categories, that the Lender wants you to provide. A category might have 1 or many documents.
Working Example
In the following screen shot, I have a checklist that has been created, with 8 Categories, and a total of 20 documents that need to be provided, across the Categories:
As you upload and satisfy documents, the Count will update
As you drag across and attach documents to your checklist requirements, the Count will update to record the documents against the Category and Document Count.
Here I have added a document that was the only requirement for the Category, so both my Document and my Category count has changed:
However in this image, I have uploaded 2 documents, but I have not completed the Category: