$0
--
- 3 items (or less) are missing or damaged.
- Didn't like the substitutions.
- Didn't like the quality of a few items.
- Didn't get a coupon or sale price: We need to give them store credit for what we owe them, but no extra Courtesy Credit.

$5
--
- 4 or more items are missing or damaged
- Charged for items they didn't order and didn't receive.
- Bad interaction with employee or delivery person.
- Delivery is an hour or more late.
- Customer is stressed about dinner plans being ruined. 

$10
--
- The customer is upset and you don't think $5 is enough of an apology.
- Delivery was rescheduled and now the customer is cancelling it.

$20
--
- Their delivery was cancelled by Instacart or
Kroger

Other amount 
--
- The customer was treated very unfairly and we did a very bad job.

Credits over $10 should be rare. Any credit above $30 needs specialist approval.
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