Variability #1

It is recommended to not set the temperature of your home hot water heater above 60°C.  Doing so may not affect adults, however children's skin is much more susceptible to burning.  This variability is therefore unacceptable because a child could be injured unsuspectingly.  Aside from the safety concerns, a variation of this magnitude might for some people be uncomfortable.  This variability in unacceptable.

Variability #2

A two degree variation will maintain the hot water within reasonable limits, and the magnitude of the variation is not significant.  This variation is realistic and acceptable.