How it is measured
Positions, fills, cash and the clock come from alpaca, the broker's own CLI. Realized P&L is rebuilt by matching every fill against the contract it closes, at average cost — not taken from a field.
Fees are read from the account's own bookings — every FEE activity the broker recorded, summed — not from a rate. An earlier version of this page assumed the OCC clearing fee of 0.025 per contract and was right until the regulatory charges settled after the first close, at which point it was short by 7.37.
What this is not
A snapshot, not a feed. The page reloads the latest published snapshot when you open it; the stamp above says which one you are looking at.
A paper account. Fills are simulated against live quotes, so slippage is the broker's model, not a filled book.
Source, and the log of what broke live