I could do with some help on the retention policy settings please...

Basically, I'd like to keep all versions of a file less than a month old. If there have been no changes, then I need to keep the latest (current) version of the file, regardless of how old it is. I think I'm OK with the settings for that, do I just need to set "delete versions older than 1 month from backup date" and "always keep the latest version" ?

If I did want to only keep a specific number of versions, I believe I'd set "keep number of versions for each file" - but how does that interact with the age setting? If a file changed regularly and hit the number limit before the age limit, would the earlier versions be removed to keep the version count down? Conversely, if the file didn't change very often, would versions older than the age limit be removed even if that meant being below the "number of versions to keep"?

When a file has been deleted from the system, I need to keep it in the backup storage for a month. I think this is "delay purge" and "delete files that have been deleted locally" settings, but I've never managed to understand what they mean and how to use them. Can anyone help me with these? The other thing that confuses me about them is when I'm configuring a hybrid backup with a NAS for local storage and an Amazon Glacier account for Cloud storage, the retention policy page doesn't have a "delete files that have been deleted locally" setting, only the "delay purge" (doing a local storage only, I get both options)

Please can anyone help me understand these settings and offer any advice on how to configure it for my requirements?

Thanks,