Value-added tax (VAT) or goods and services tax (GST)
AdSpecs can have two VAT Types, either "normal" which equals 1 or "reduced" which equals 2. Therefore the Ad Spec defines, which type of VAT should be used when this product is sold in a Media Campaign.
Define in the Ad Spec the VAT Type:
VAT Type in the Ad Spec is compared later with the custom setting VAT and the Country/State of the Media Campaign and your Org to define which VAT record should be used.