Once you have purchased Shared Datacenter Proxies, you can create proxy traffic limits by logging in to the Oxylabs dashboard and proceeding with the following steps:
Select Usage Limits within the menu;
Click Create rule;
Select Shared Datacenter Proxies as the product;
Choose the proxy users that you want to limit;
Pick the period for limits (daily, monthly, or lifetime);
Set the traffic limit;
Click the Create limit rule to save your settings.
You can also decide what happens when the limit is reached. Nothing will happen by default, but you may receive email notifications and/or deactivate the proxy user.
See this visual guide on how to set up proxy traffic limits: