16 core is a minimum only. The 2 and 8 core packs accommodate the many different configurations of processor core counts. More here
https://www.microsoft.com/en-us/UseTerms/Retail/WindowsServer2019/DatacenterAndStandard/Useterms_Retail_WindowsServer2019_DatacenterAndStandard_English.htm
and here
https://www.microsoft.com/en-us/licensing/product-licensing/windows-server
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