FP numbers are (roughly) stored in the form m×2^e (m = mantissa, e = exponent). When numbers can't be represented exactly, m is rounded. My guess is that these

FP numbers are (roughly) stored in the form m×2^e (m = mantissa, e = exponent). When numbers can't be represented exactly, m is rounded. My guess is that these numbers end up being encoded as 4999999999999999×2 and 4999999999999999.5×2, where the latter is rounded up to 5000000000000000×2.