Knowledge is knowing facts.
Understanding is knowing how to know.
We can have knowledge of understanding if we have acquired new understanding. Then we know how to know it.
If we have knowledge only from one understanding, we do not know how to know understanding.
If you do not understand the above, consider the possibility that this might be an example of not knowing how to know.
Entertaining this possibility means to feel anxiety in the face of dread. Dread is why babies cry.
Generally, we just know with whatever understanding we happen to have. That is, we misunderstand. We follow intuitive impulses away from anxiety to preserve the understandings we have, which keep us sane — which in fact are our sanity. We choose misunderstandings over understandings to avoid the trauma of birth.
The ability to recognize the experience of not-knowing-how-to-know is the key to acquiring new understanding.
To know that you do not know is good — but to act in faith that you might one day understand and know is much better. This is the sole value of humility. All other kinds of humility are submissiveness, practical responses to weakness, or fear of responsibility.