[thg]

The traffic limit is outbound only. There is no limit on inbound / internal traffic. So even if they were to hit you with a 5TB / month limit, you'd be just fine.

https://docs.hetzner.com/robot/general/traffic/ (bottom of the page)

[immibis]

This is correct. No idea why it was flagged. Hetzner only counts outbound traffic.