It depends on your subscription plan (you can see more details about our plans and pricing here: https://ahrefs.com/pricing-plans).
Users of both Advanced and Agency plans get updates of their tracked keywords every day. The Standard Plan allows our clients to see updates every three days. And the Lite Plan provides weekly updates. (See the screenshot below.)
Please, pay attention that we don’t provide an ‘update on demand’ option at this moment, meaning you can’t force-run our keyword rankings checker to get updates more frequently than it is allowed by your subscription plan.