When reviewing Flowlogs for a host on a private subnet in an AWS VPC that routable IP addresses are being rejected. How is that possible? I expect IP addresses from the private subnet could be rejected but not routable IP's

This is an example of the flowlog:

12:24:40 2 redacted eni-obfuscated 149.28.xx.xx 10.55.27.62 53501 22 6 1 40 1539951880 1539951940 REJECT OK

13:22:41 2 redacted eni-obfuscated 60.51.xx.xx 10.55.27.62 60375 8081 6 1 40 1539955361 1539955421 REJECT OK

13:39:41 2 redacted eni-obfuscated 221.229.xx.xx 10.55.27.62 9090 22 6 1 40 1539956381 1539956441 REJECT OK

The VPC layout contains a public and private subnet. The private subnet routes outbound to the Internet through an AWS NAT Gateway. The public subnet contains a bastion host that is used to connect to the private host.

The bastion server has a security group that only allows in port 22 from specific IP addresses (a.b.c.d/32).
The host on the private subnet has a security group that allows only ssh in from the bastion host, and all traffic from the private subnet.

So where is this coming from? On the bright side no IP addresses I don't expect are being accepted.