Report Date range seems fixed

First post and I'm pretty sure that this is newbie error

Running FAZ 6.4.4

Playing about in reports but so far I can't seem to change the date range.

Pick a shipped report 'Web Usage Report'

Click settings and choose 'last 14 days'

Run report - I get the default 'this week'

Check settings - still says Last 14 days

Tried cloning the report, renaming and changing settings - it still only gives me the current week.

I'm missing something basic, aren't I...