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Match the contract details
An original spread holds one call at strike 90 and writes one call at 110, on the same underlying, unit quantity and expiry. Those facts allow the two terminal amounts to be added at one price. Different expiry dates would require a different record.
Apply holder and writer signs separately
The first leg contributes max(S−90,0); the second contributes −max(S−110,0). Adding both as positive amounts would construct two long calls rather than the supplied spread.
Keep a separate premium bridge
If the long premium is 12 and the short premium is 4, the initial net cash flow is −8. Simple profit equals combined payoff minus 8. The net debit is not the sum of the two positive quoted premiums.
| Leg | Payoff sign | Premium cash flow |
|---|---|---|
| Long 90 call | Positive holder amount | −12 |
| Short 110 call | Negative holder amount | +4 |
| Combined | First minus second | −8 |
Do not infer valuation from payoff addition
The terminal algebra describes the supplied positions. It does not calculate fair premiums or establish that the position is suitable for an investor. Keep pricing, funding and exercise assumptions outside the simple payoff sum unless explicitly supplied.