Your thinking is correct, that is if my thinking is correct, how many people make 1 way of thinking correct?

 

The fact that the archive process on the next scheduled run will process the first 1000 items in the mailbox (this is default, changed in mailbox archive task properties), hence the low count in 'size of items ready to archive' as opposed to 'total size of archivable items'

 

If you are just starting and want to remove large items then this is set in the archive policy properties.

 

M

Let me get this straight, ultimately over a period of several archive runs all the items under "'total size of archivable items" will be archived it will just take several runs because only 1000 items are archived at a time?

Yes,

 

This way the possibility of all mailboxes being touched is a good one.

 

The date based archiving will start from the beginning if the archive window is still open. Quota bases archiving will only make one run. (Not sure why).

Not only that, but there is a default limit of 200 mail items from each mailbox to be processed at a time.

This is all to try to prevent EV from getting overloaded

 

If this is a new installation, then you should be "bottom slicing" - taking the oldest stuff out first, then potentially closing the partition and then taking the next oldest slice out. This way in two years time you will know what you might have considered as "too old" two years ago and might be a candidate for secondary or tertiary storage.