Work Step by Step
If a value is unusual, then it is more than two standard deviations far from the mean. $Minimum \ usual \ value=mean-2\cdot(standard \ deviation)=12.19-2\cdot0.11=11.97$. $Maximum \ usual \ value=mean+2\cdot(standard \ deviation)=12.19+2\cdot0.11=12.41$. Here, $11.9<11.97$, therefore the value is unusual, because it is smaller than the minimum usual value mean.