Update Get-DataRetentionReport.md

Issue #10291

Author: chrisda

exchange/exchange-ps/exchange/Get-DataRetentionReport.md

@@ -106,6 +106,8 @@ The StartDate parameter specifies the start date of the date range.
 
 Use the short date format that's defined in the Regional Options settings on the computer where you're running the command. For example, if the computer is configured to use the short date format mm/dd/yyyy, enter 09/01/2018 to specify September 1, 2018. You can enter the date only, or you can enter the date and time of day. If you enter the date and time of day, enclose the value in quotation marks ("), for example, "09/01/2018 5:00 PM".
 
+The StartDate value can't be older than 92 days from today.
+
 ```yaml
 Type: DateTime
 Parameter Sets: (All)