In summary:
Original source data = 100 GB Total retained data = 100 GB + (100 GB * .10 change rate * 15 days) = 100 GB + 150 GB = 250 GB VMCTLMC data required = 250 GB * 0.002 VMCTLMC estimate = 0.5 GB
Remember that this is an approximation.
https://www.ibm.com/support/pages/understanding-metadata-vm-backups