You will need to modify your report to only list "new" servers. You can add the following criterion to tblAssets.firstseen to only list machines that were first discovered in the last day: > GetDate() - 1
Example:
Select Top 1000000 tblAssets.AssetID,
tblAssets.AssetName,
tsysAssetTypes.AssetTypename,
tsysAssetTypes.AssetTypeIcon10 As icon,
tblAssets.IPAddress,
tblAssets.Firstseen,
tblAssets.Lastseen,
tblAssets.Lasttried
From tblAssets
Inner Join tblAssetCustom On tblAssets.AssetID = tblAssetCustom.AssetID
Inner Join tsysAssetTypes On tsysAssetTypes.AssetType = tblAssets.Assettype
Where tsysAssetTypes.AssetTypename = 'windows' And tblAssets.Firstseen >
GetDate() - 1 And tblAssetCustom.State = 1