Doc Wording change

Currently the definition of the billing plan history period is as show below in the hosting documentation

History period
The period of time during which the system stores the unit history, unit and user logs, and so on. You can indicate this time period either in days or months (select from the dropdown list). For example, if the value is 100 days, the messages older than 100 days are deleted automatically.
You can also redefine this parameter for every account separately.

I think that there needs to be a line added to address the hierarchy issue. That is, that an account higher in the hierarchy cannot have a shorter retention than the account below it.

I know there is a reference to it in the architecture description but not all users will go to that.