Most of the time when using Leadfeeder, you will see more visits on your site than you see leads in Leadfeeder. That's all normal and ok, as, for example, Google Analytics visits and Leadfeeder leads are different units of measurements, they most likely differ and therefore should not be compared to each other - like you cannot compare miles to gallons.
In most cases, the reason is any of these:
Sometimes Unique Visitors can only be identified as Internet Service Providers (ISPs) and Leadfeeder filters out ISPs so you don't see them as leads in Leadfeeder.
Multiple visits from one company show only as one lead – this means that e.g. multiple visits by people in the same company might show only as one lead.
The same person can visit more than once using different browsers. These would show as more than one Unique Visitor but in Leadfeeder would only show as one company.