Begin from report:
Select Top 1000000 tsysAssetTypes.AssetTypeIcon10 As icon,
  tblAssets.AssetName,
  tblAssetCustom.Model As [Device  model],
  tblCustDevPrinter.AssetID,
  Floor(tblCustDevPrinter.TonerRemaining / tblCustDevPrinter.TonerMaximum *
  100) As [Remaining %],
  tblCustDevPrinter.Tonername,
  tblCustDevPrinter.Lastchanged
From tblCustDevPrinter
  Inner Join tblAssets On tblCustDevPrinter.AssetID = tblAssets.AssetID
  Inner Join tsysAssetTypes On tblAssets.Assettype = tsysAssetTypes.AssetType
  Inner Join tblAssetCustom On tblAssets.AssetID = tblAssetCustom.AssetID
Where Floor(tblCustDevPrinter.TonerRemaining / tblCustDevPrinter.TonerMaximum *
  100) >= 0 And tblCustDevPrinter.TonerMaximum > 0 And tblAssetCustom.State = 1
Order By [Remaining %]