You may have a misunderstanding of double precision floating point numbers, Fidel. The number 2.2204e-16 is the value of the least bit for a number that lies between 1 and 2, which is to say it is equal to 2^(-52). However, for smaller numbers, the least bit becomes correspondingly smaller. For example, if a number lies between, say, 1/32 and 1/16, the least bit will have a value of 2^(-57) = 6.9389e-18, representing a more precise value in absolute terms. The basic idea is that double precision (matlab's 'double') numbers have 53 bits to use for their significand (mantissa), so the ratio between the least bit value and the value of the number is always between 2^(-52) and 2^(-53), or roughly sixteen decimal places.
It is only when double numbers are smaller than 2^(-1022) where they become 'denormalized' that they begin to lose the sixteen decimal place precision, and these are exceedingly small numbers.
