Bracket fungi

I allowed this piece of fungi (?) to grow at my window ledge for a few weeks. In the beginning it was not significant, It looked like a small piece of lime concrete which had fallen at this spot where the water fell down the eaves during monsoons. After a week or so, the central area grew to around 3 mm and gradually darkened and gained in depth. After another week, it started taking the cup shape and gained striations on the outside. As water continued to trickle down for another week in slow progression, the shape become larger though less symmetric and the shaded whorls (?) were visible, darker shades towards the centre and fading towards the edges.