When you select a vendor, the claims and reminders will be automatically inherited from the vendor, but you can change this if you wish.
Notice type specifies whether the notice is a cancellation, claim, reminder, priority claim or priority reminder.
Level shows whether the notice is the first, second, third, etc.
Period specifies when the notice is to be sent. For monographs the period is relative to the Expiry date. For subscriptions the period is relative to Date order expected in the Issue/Order Status details.
Delivery specifies how the notice is to be delivered.
If you've changed the claims and reminders you can click Load Vendor Default to inherit the defaults again.