Here is a little piece of code that can be used in a notification action to improve formatting of Disk Statistics sensor results:
Notification Script
Data Disk Free: ${str:substringBefore(result.statistics['greenlight.disk.data.free.pct']*100, '.')/100}% (${str:substringBefore(result.statistics['greenlight.disk.data.free.megabytes']/1024*100, '.')/100} GB)
Program Disk Free: ${str:substringBefore(result.statistics['greenlight.disk.executable.free.pct']*100, '.')/100}% (${str:substringBefore(result.statistics['greenlight.disk.executable.free.megabytes']/1024*100, '.')/100} GB)
It will result in an output like this:
Data Disk Free: 5.9% (3.59 GB)
Program Disk Free: 5.9% (3.59 GB)