Hi @Farzana Mustafa,
Welcome to the Microsoft Q&A Platform! Thank you for asking your question here.
Each instance has its own dedicated 4 vCPUs, and they are not shared among instances.
So, if you have a VMSS with 3 instances, each with 4 vCPUs, the total quantity of cores would be:
3 instances x 4 vCPUs per instance = 12 vCPUs
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