The easiest way would be to add a new
Data report or
Chart report widget to your Dashboard which you use in combination with a custom report. The following report lists Mac assets counted by their asset state. If you save it under a name beginning with "Chart: ...", you will be able to use it for a Chart report widget.
Select Top 1000000 tblState.Statename,
Count(tblAssets.AssetID) As Number
From tblAssets
Inner Join tblAssetCustom On tblAssets.AssetID = tblAssetCustom.AssetID
Inner Join tsysAssetTypes On tsysAssetTypes.AssetType = tblAssets.Assettype
Inner Join tblState On tblState.State = tblAssetCustom.State
Where tsysAssetTypes.AssetTypename like 'apple mac'
Group By tblState.Statename
Order By tblState.Statename