About Deduplication in netbackup

We have planned to keep our monthly and yearly backups in to disk. Planning to use netbackup MSDP. Our current backup size is 10TB. Every month full bakcup and 1year retention. My question is first time it will be 10TB and second month will it take dedupe data and keep it for 12months or it will take entire 10TB plus additional changes (say example 200GB changes as every month)10.2TB and keep it for 12 months.If its 10.2 tb means means my total space will be10.2 * 12 = 122.4TB.

Thanks in Advance.