Currently Disk space alerts are very poor in their verbiage. They come as a "Counter" of "Used Disk Space". However, it doesn't say how much of that used space is of the entire space available. No other monitoring tools that I'm aware of do this. They all give either a percentage left or how many GB remaining on a disk. Even when you set the Critical and Warning for the alert, it asks for how many GB remaining.
This doesn't provide a sense of urgency if just stating the used space. We have many servers, and we may not know the exact disk size of the top of our heads.
Which, also...the alert does not state if its at a Critical alert or a Warning alert, so I also don't know how critical the disk space issue is.