[Ntop] [NTOP] NTOP RRD

[Nascean]

Hi all,

I am having some difficulty understanding the RRD options in NTOP.  
Would someone be able to explain why the dump hours able to have 48 or  
72 hours as a value?

If i want to keep 3 months data, is the below correct?

Dump hours 72
Dump days 90
Dump months 3

Thanks very much.