Fell out of DOCS-10381. Procedure at https://docs.atlas.mongodb.com/security-vpc-peering/ has the following errors and omission:

• Step 3 suggests illegal VPC cider blocks for the VPC ID. AWS will not accept 10.0.0.0/8 and
  172.16.0.0/12. /16 is the lowest acceptable prefix.
• Separately, step 6 neglects to inform the user that they must also associate the peering connection id from Atlas with the Atlas Cidr id.