Inverse (Coin-M) example:
You buy 100,000 BTC/USD (PI_BTCUSD) contracts at $35,000. Each contract is worth $1, so this is a $100,000 notional position. The price rises to $40,000 and you sell.
(1 / Entry Price − 1 / Exit Price) × Position Size
(1 / 35,000 − 1 / 40,000) × 100,000 = 0.3571 BTC profit
Linear (Multi-M) example:
You buy 1,000 SOL/USD (PF_SOLUSD) contracts at $85. Each contract is worth 1 SOL. The price rises to $105 and you sell.
(Exit Price − Entry Price) × Position Size
(105 − 85) × 1,000 = $20,000 USD profit