AWS Transit Gateway Site-to-Site VPN Dynamic routes limit of 100. Is it per Connection or Aggregate?

The 100 routes from on-premises is per VPN attachment and can scale out with multiple VPN attachments. We'd typically recommend route summarization or using a default route for situations where a customer wants to advertise over 100 routes. If neither of those options will work, the customer can use multiple VPN attachments and splitting the routes. The 10,000 route limit is the total per TGW. Another thing to look out for here is that you can advertise up to 1,000 routes to on-premises through VPN. Make sure you don't have more routes than that in the TGW route table, as the max routes advertised from a Site-to-Site VPN connection on a TGW to a customer gateway device: 1,000