nextGaussian() will draw samples from a normal distribution with mean 0 and std-deviation 1, so if you want mean 1 hour and std-deviation 15 minutes you’ll need to call it as nextGaussian()*15+60.
From the docs for Random.nextGaussian():
Returns:
the next pseudorandom, Gaussian (“normally”) distributed double value with mean 0.0 and standard deviation 1.0 from this random number generator’s sequence