The concluding part of the last verse says:

وَأَحْصَىٰ كُلَّ شَيْءٍ عَدَدًا (...and has comprehensive knowledge of everything by numbers....72:28). In other words, Allah alone encompasses the perfect knowledge of everything and keeps a meticulous count of it. He has the knowledge of the exact number of particles in the mountains. He has the knowledge of the exact number of drops in all the oceans of the world. He has the knowledge of the exact number of drops in every rain. He alone has the knowledge of the exact number of leaves on all the trees in the world. Thus it is made clear that the totality of the knowledge of the Unseen is reserved exclusively for Allah, so that there should be no misunderstanding about the above 'exception' clause.

The question of the Unseen Knowledge is fully discussed under [ 27:65]

قُل لَّا يَعْلَمُ مَن فِي السَّمَاوَاتِ وَالْأَرْ‌ضِ الْغَيْبَ إِلَّا اللَّـهُ

Say, "No one in the heavens and the earth has the knowledge of the Unseen except Allah." [ 27:65]