When adding an alert rule on a VM, the display for "% Committed Bytes in Use" or "% Free Space" metrics show the units under "Threshold" as "Count", but this should be "%". It also shows in the Condition column when looking at a list of Alerts (for example, "> 80 Count" instead of "> 80 Percent").
This seems to be a bug with Portal display for those two metrics and should be fixed.