This is just wrong? The largest Float64 is 1.7976931348623157e308 and the smallest is 5.0e-324 They multiply to ~1e-16.
That's a subnormal [1]. The smallest normal double is 2.22507e-308:
DBL_MIN = 2.22507e-308
DBL_TRUE_MIN = 4.94066e-324
[1] https://en.wikipedia.org/wiki/Subnormal_number