I’m not subtracting, I’m multiplying fractions. Half stayed on-shore; of that half, half went into the sky. That’s half of a half which is a quarter, which I’m

I’m not subtracting, I’m multiplying fractions. Half stayed on-shore; of that half, half went into the sky. That’s half of a half which is a quarter, which I’m rounding up to a third because later I take the reciprocal so the higher proportion is a more conservative estimate.