A calendar's Max L looks too small

What you see. A calendar’s Max L is small, and its Expiry curve is curved instead of flat-sided.

Why. By design. Back legs keep time value at the front expiration, so the curve bends. Across expirations, Max L is the lowest P&L inside the chart’s price range, not an exact bound.

What to do. Treat it as the debit-scale risk, not a guaranteed floor. See Max profit and max loss.