Explanation
Introduction to Azure managed disks
https://docs.microsoft.com/en-us/azure/virtual-machines/windows/managed-disks-overview "Using managed disks, you can create up to 50,000 VM disks of a type in a subscription per region, allowing you to create thousands of VMs in a single subscription. This feature also further increases the scalability of virtual machine scale sets by allowing you to create up to 1,000 VMs in a virtual machine scale set using a Marketplace image."