Johnny.Decimal, a system for organizing documents in a structured way

I've started decluttering my digital life and deleted nearly all emails from my Gmail archive as a starter. Next low-hanging fruit is the files/documents scattered around my local system, Dropbox, Google Drive, Evernote, what have you. Johnny.Decimal seems like a good template to start giving a unifying organization structure to them.

From the Areas & categories page:

First, we divide everything in our system in to (at most) ten large buckets of stuff. We call those our areas, and we assign each area a range like 10-19, 20-29 … 90-99.
Then, within each area, we break things up again in to (at most) ten more buckets. We call them categories and we assign them numbers like 11, 12 … 19.

This gives us up to 100 categories of things, up to 10 groups of categories.

Finally, we assign each individual thing in our system to a category, and give it a unique number. We start at .01 within each category, and work our way up through the numbers

Each thing will be referenced with a Johnny.Decimal number in the format of [category number].[thing number]. As each number is limited to two digits, the system can handle up to 10,000 things.

As the screenshots in the Saving files page clarify, you can store multiple files under each thing. Recreating the first screenshot in ascii...

> 10-19 Finance
v 20-20 Administration
  > 21 Company registration
  v 22 Contracts
    > 22.01 Cleaning contract
    v 22.02 Office lease
      Security bond details.xlsx
      Signed lease agreement.pdf
      Terms & conditions.doc
  > 23 Staffing
> 30-39 Marketing
> 40-49 Sales

Use date-based numbering when it makes sense.