The quota meters on the System Information page (in the Virtualmin Framed theme) are a nice visual indicator of the current usage. However, since they all share the same scale, this feature is currently not useful for domains with smaller quotas.
For example, our server has a domain with a large quota, such as 5 GB, as well as many domains with small quotas, such as 50 MB. The 5 GB quota sets the bar scale very high, so the rest of the domain quotas basically show up as only a few pixels with the rest of the bar as just gray space, which isn't useful at all.
These scales ideally should be displayed as percentages with 100% being the max, instead of as using fixed scales based on the size of the largest domain. The numeric column on the right still shows the actual size, so that should suffice in setting the context of the scale.