From the Oracle cloud infrastructure always free service document site, it says this:
All tenancies get two Always Free Compute virtual machine (VM) instances.
You must create the Always Free Compute instances in your home region.
Details of the Always Free Compute instance Shape:
VM.Standard.E2.1.Micro Processor: 1/8th of an OCPU with the ability to use additional CPU resources
Memory: 1 GB
Networking: Includes one VNIC with one public IP address and up to 480 Mbps network bandwidth
Operating System: Your choice of one of the following Always Free-eligible operating systems:
Oracle Linux (including Oracle Autonomous Linux) Canonical Ubuntu Linux CentOS Linux
The VNIC with one public IP address and up to 480 Mbps network bandwidth describes the network speed not the amount limit from my point of view. So the question is how much bandwidth one always free compute can use freely for a month or some peroid of time.
Oracle's press release for Always Free launch explicitly mention
The new Always Free program includes the essentials users need to build and test applications in the cloud: Oracle Autonomous Database, Compute VMs, Block Volumes, Object and Archive Storage, and Load Balancer. Specifications include:
...
- 1 Load Balancer, 10 Mbps bandwidth
- 10 TB/month Outbound Data Transfer