Hi, why does the ear not look symmetrical?

I believe sometimes Blender doesn't quite mirror things with 100% fidelity and things add up and before you know it you have one ear longer than the other. Don't quote me on that though, but I think that's how things go. Fortunately there is a symmetrize option,you just need to specify the direction you wish the symmetry to be applied at and hit Symmetrize.

Omar is exactly right. Especially with dynamic topology, symmetry is rarely perfect since geometry is being generated on the fly. The symmetrize button will make it perfect. Non-dynamic-topology sculpting is usually better about maintaining symmetry when sculpting