It's quite clear. If you offer a tracked service, which is anything except an untracked letter, you must upload tracking for at least 95% of those items.

An example (me) - 50% are untracked letters. I must upload tracking for the 50% that go as parcels. The 95% is based on that 50% of my sales, not total sales.

If you have synchronisation issues, it might pay to upload the tracking manually.