Symmetric bell shaped curve.
This distribution is popular for setting timing and label values as the likelihood of extreme high or low values is very low and can be controlled via the standard deviation.
For instance, it is used for durations of operations when variability is low (e.g. operation usually takes 24 minutes but sometimes varies as low as 21 and as high as 27).
95% of samples are within mean +/- 2 “standard deviations”. In the above case you might use:
Std Dev: 1.5