Count the crowd before you pay.
Privacy is a crowd. This counts the one a crossing would leave in on the Zcash side: every exit from Zcash's shielded pools, read from the public chain. No wallet is needed, and the size you type is counted in your browser: it is sent to nobody.
Each dot is one exit in the window, placed by its size. The lit ones are within 10% of yours.
Live, from public blocks.
An exit = a transaction with shielded parts, no transparent input and at least one transparent output. Its size is the sum of those outputs. Windows are counted in blocks: 24 hours is the last 1,152.
Layer 1 · Zcash
Somebody who reads only the Zcash chain has to match an entry to one of these exits. This crowd is borrowed: it was there before any crossing, and it is the number above.
Layer 2 · the rail and Robinhood Chain
Somebody who also watches the swap rail pay out on Robinhood Chain sees a smaller crowd. So read the grade as the Zcash side only, and treat it as an upper bound: against that second observer what protects a crossing is the wait, uneven pieces and separate wallets, not this number.