Hummingbird says browser caching enabled but it seems not

Hi there,
Hummingbird tells me this:

Your browser caching is already enabled and working well

But when I look at the settings, there is a discrepancy between the current and the recommended value.
If I save it, nothing changes in the interface, the values stay the same, no matter what I choose as the value.

Any idea what may be wrong?

Warm regards,
8 days 30 days