Mac OS data is stored in tblMacOSInfo. A sample report can be seen below.
Select Top 1000000 tblAssets.AssetID,
tblAssets.AssetName,
tblAssets.IPAddress,
tblMacOSInfo.SystemVersion,
tblAssets.Firstseen,
tblAssets.Lastseen,
tsysAssetTypes.AssetTypeIcon10 As icon
From tblAssets
Inner Join tsysAssetTypes On tsysAssetTypes.AssetType = tblAssets.Assettype
Inner Join tblMacOSInfo On tblAssets.AssetID = tblMacOSInfo.AssetID
Order By tblAssets.IPNumeric