Currently, when on the main storage tab of the admin portal, there are a number of additional filters/search terms that may be applied. No filter is available for "Domain Type". For example, there is no way to setup the search bar such that only master storage domains are shown. If a domain type filter is added, the dashboard can use it to filter the specific storage domain types displayed when a user clicks through from the Data Storage Domain inventory card. Without the filter, users have gotten confused because the Data Storage Domain inventory card only shows data domains. When they click through (by clicking on the card's title) they may see more storage domains then what is counted on the card. Dashboard only counts Master and Data storage domains types in its queries. See BZ1420448, especially 1420448#c6 for how this relates to ovirt-engine-dashboard.
Closing old RFEs. Most likely storage domain types will be unified in the upcoming version(s). If relevant, please re-open and explain why. As always- patches are welcomed!