You can apply a precision count to all numeric values on the chart using the decimals attribute in the globals object.
globals:{
decimals:1
}...
If you want to apply decimal precision to only a specific portion of the chart you would apply the decimals attribute to the object you want to modify. Lets use valueBox.
plot:{
valueBox:{
decimals:1
}...
}...
To see the difference between the two examples, hover over then nodes and look at the value above the bar.