Hi,
Mathematics is an abstraction of reality, it's not the reality itself. Supposedly it originated from simple counting and probably then advanced to include comparison.
It's probably more accurate to say that it was invented because of the counting but interestingly nothing we calculate matches anything in the universe *exactly*. Everything seems to be an approximation. Even counting is an approximation. If i go to the store and buy 2 apples and you go to the store and buy two apples. we both have 2 apples, but that's only an approximation of what we really have in each of our possessions. I might have bigger apples than you, or maybe one bigger and one smaller, and your apples will be different sizes anyway.
No one on this earth knows the true relationship between a circle and its circumference, they only know approximations. Some know better ones than others, but there's not one person that can tell you the exact relationship. In fact, because of this the relationship has to be given as a symbol rather than an actual exact number.
All four sides of a square are the same length. Funny thing though, there's not one perfect square anywhere we know of in the universe. And when we go to measure something like that we have to resort to statistical means to approximate where the boundaries are, which brings us right back to yet another approximation. Measure the distance between two pool balls sitting on the pool table. What's the distance. First, how do we measure it? We get a ruler and stretch it across the table from one to the other, but we find we cant really get the end of the ruler to touch even one of the balls because at the surface the forces wont let the two touch, and that's only one of the many problems that come up, so we have to approximate again.
But surely we can calculate the time it takes the earth to make one revolution around the sun right? Here comes approximation again, and why our calendar is not accurate over many years but needs constant adjustment.
So in the end it's all only perfect in theory and theory is invented. Unless maybe we can find one of the moons of an exoplanet counting sheep before it goes to sleep