Each event records the vault's collateral and debt after it, and the debt is what the Vat states: the vault's normalized debt × WBTC-B's rate accumulator at the block. So the stability fee between two events is exact, the debt just before an event less the debt after the one before, and the bar draws it dashed as Stability fee. DAI is counted at its $1 face.

Between events the debt grows in a straight line from what an event recorded to what the next event's rate makes of it, and after the last event to the vault's live read, which is today's figure. Maker adds the fee to the rate in lumps, when someone calls Jug.drip, so a day between two events is stated to within how the fee was dripped between them.

The collateral is valued at Maker's oracle price for WBTC-B at the close of each day (Vat spot × Spotter mat, the price the liquidation check uses, one hour behind the market), recorded once a day in Rails' daily price store: each event at its day's price. Market move is the change in that price since each flow.