Hello,
If you are using Free Tier, the limit is 1 GB network egress from North America to all region destinations (excluding China and Australia) per month. Please see [1] section 'Compute Engine'. If this is not the case, the network egress monthly usage will depend on your configured network Tier. I have found this public documentation [2] where is explained the network usage in TB (up to 500 TB/month for Standard Tier) and its pricing for specific regions. Please note that the Network ingress remains free for both tiers.
Additionally, and if needed, you can always reach out to support team for any concern or additional question for your use case in [3].
I hope this information helps.