Hi Priyesh,Each virtual drive needs to be the same size, and so depending on whether you choose to allocate 100GB, or 200GB per each drive, those columns tell you how many disks you need to allocate. For example, lets say you choose to set the disks at 100GB, If you choose spin up a 4 core VM, then you would allocate 2 of the 100GB drives. On the same token, if you decided to use 200GB drives, then you would only need to allocate 1 drive. The choice between 100GB and 200GB is up to you. Do note that some models when you go into the higher core counts cannot be run with just 100GB disks.
I hope that helps!