Comment by camel-cdr

Usually floating point numbers are defined as `1.fraction * 2^(exponent-bias)`, but if the exponent is zero `0.fraction * 2^(1-bias)` is used, to allow representing very small numbers.

IIRC I also explained it here: https://m.youtube.com/watch?v=VHJUlRiRDCY&t=2774s