On the review team, there's likely to be different people reviewing different credits, based on their area of expertise. The summary narrative helps those different players understand the big picture of the project and can often prevent a lot of misunderstanding and mis-interpretation of your credit strategies. If you imagine what key information will help a specialist diving into a few specific credits understand the relevant context they'll need to understand your submission, that's what you want to aim for.

As far as the numbers, provide your best guess if you have one, or leave some blank, but realize that in their aggregate those numbers will hopefully inform and guide future decision making.