Ok...This particular quadratic is written in the form
which is just a
transformation of the basic
quadratic which has a vertex at (0, 0). The two most important transformations for your question are the value of b and c.
The b value tells you how far to the right the vertex has moved, and the c value tells you how far up the vertex has moved.
In your case, the b value is 1 and the c value is 6.3.
So your vertex is at (1, 6.3). Since this is a coordinate it has the form (t, h) for your equation.
With this information, can you tell me when the highest point (i.e. the vertex) is reached?