Lord (William Thompson) Kelvin,
"I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind." – from Popular Lectures and Addresses
Lord Kelvin was my hero when I was younger. This was my favorite quote. I will not presume to tell you what Lord Kelvin meant, in context, when he wrote this. I think it would be better for you to read his original works if that is what you seek. I can tell you what it meant to me. I believed that only something which can be measured, experimented upon, and verified could truly be known. That ruled out God or anything "supernatural". There was no super nature.
Throughout my life, heroes have proven fallible. Most are wiser than I, but limited and fallible none the less. Kelvin was very insightful, but he was dead wrong about a lot of things. Much was not known in the 19th century, such as Energy=Mass times the speed of light squared. Einstein, who was able to develop that equation, struggled with quantum physics. I'm sure he understood quantum physics a lot better than I do, but as Einstein ran out of steam, other physicists pushed forward.
Science as a field of knowledge is a subset of all that can be known scientifically. Why else would scientists be working so diligently to expand the field? Much of our current knowledge will seem as antiquated as Lamarck's theory of heredity, which proposed the inheritance of acquired traits. Lamarck deserves respect as a scientist, but his theory did not stand. Newton deserves great respect as a scientist, but there was much he did not know. Special and general relativity, for example.
So current science is a subset of all that can be known scientifically. Things will be learned that surprise us and discredit some of our best efforts to date.
What can be known "scientifically" is also a subset of what can be known by humans. I love my wife. Measurements and experiments would be ludicrous. I love my wife. It is something I know. I do not need science to know it. I exist. I once wondered how I knew that. I gave up wondering after a while. I simply know that I do. The universe exists. I'm quite certain about that as well.
God exists. God told me so. I resisted hearing God for a very long time. I had to be profoundly humbled before I was able to hear God say "I am not your concept, you are my concept". I once believed that the universe just existed, and needed no creator. I was wrong. It is the creator who needs no creator. I have knowledge that transcends science. To those who would deny my knowledge, I simply ask this. How can you be so sure?